Wikipedia:Citing sources

For a simpler introduction to citing sources, see Wikipedia:Referencing for beginners.

Various shortcuts redirect here; you may be looking for Wikipedia:Reference Desk or Wikipedia:Citing Wikipedia.

"WP:CS" redirects here. WP:CS may also refer to Wikipedia:Clean start, Wikipedia:Cheatsheet, Wikipedia:WikiProject Computer science or Wikipedia:Use common sense.

This page documents an English Wikipedia content guideline. It is a generally accepted standard that editors should attempt to follow, though it is best treated with common sense, and occasional exceptions may apply. Any substantive edit to this page should reflect consensus. When in doubt, discuss first on the talk page.

Shortcuts: WP:CITE WP:REF

Citations, frequently called references, are an important part of any Wikipedia article, serving to identify the reliable sources on which the information in the article is based. In most cases, citations for specific pieces of information contained in an article are given in the form of footnotes, though they can also appear within the body of an article. Citations that are indicated by a superscript number or other means in a line of text are called inline citations.

Wikipedia's Verifiability policy describes when sources should be cited, and what kind of sources are considered reliable. It requires inline citations for any material challenged or likely to be challenged, and for all quotations, anywhere in article space. However, editors are strongly advised to provide citations for all information added to Wikipedia; any detail risks being unexpectedly challenged or even eventually removed.

This page contains information on how to place and format citations. Each article should use the same citation method throughout. If an article already has citations, adopt the method in use or seek consensus on the talk page before changing it. While you should try to write citations correctly, what matters most is that you provide enough information to identify the source. Others will improve the formatting if needed.

Wikipedia guidelines
Behavioral
Assume good faith Conflict of interest Don't bite the newbies Don't disrupt Wikipedia to make a point Etiquette Gaming the system User pages
Content
Citing sources Identifying reliable sources
Stand-alone article
Notability
Discussion
Signatures Talk page guidelines
Editing
Article size Be bold Don't add the full text of primary sources Don't create hoaxes Edit summary Patent nonsense
Organization
Categories, lists, and templates Categorization Disambiguation Subpages
Style
Manual of Style Manual of Style/Lists Manual of Style/Tables
More
List of policies and guidelines

1 Types of citation
2 When and why to cite sources
3 Inline citations
- 3.1 Footnotes
- 3.2 Parenthetical referencing
4 General references
5 What information to include
6 Citation style
7 Variation in citation methods
8 Handling links in citations
9 Text-source integrity
10 Bundling citations
11 In-text attribution
12 Dealing with unsourced material
13 Citation templates and tools
14 See also
15 Notes
16 Further reading

Types of citation

A full citation fully identifies a reliable source and, where applicable, the place in that source (such as a page number) where the information in question can be found. For example: Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 1. This type of citation is usually given as a footnote, and is the most commonly used citation method in Wikipedia articles.

An inline citation means any citation added close to the material it supports, for example after the sentence or paragraph, normally in the form of a footnote.

A general reference is a citation to a reliable source that supports content, but is not displayed as an inline citation. General references are usually listed at the end of the article in a References section. They may be found in underdeveloped articles, especially when all article content is supported by a single source. They may also be listed by author alphabetically in a References section in more developed articles as a supplement to inline citations.

A short citation is an inline citation that identifies the place in a source where specific information can be found, but without giving full details of the source – these will have been provided in a general reference. For example: Rawls 1971, p. 1. This system is used in some articles; the short citations may be given either as footnotes, or as parenthetical references within the text.

In-text attribution means saying within the article text itself (not as a mere footnote) where particular statements come from. This is done especially with statements of opinion, uncertain facts, and quotations. Usually the in-text attribution does not specify full details of the source text – this is done with a footnote in the normal way. For example: According to John Rawls,^[5]... See In-text attribution below.

When and why to cite sources

By citing sources for Wikipedia content, you enable other editors and readers to verify that the information given is supported by reliable sources, thus improving the credibility of Wikipedia and showing that the material is not original research. You also help readers find additional information on the subject; and you avoid committing plagiarism (by giving credit to the source of your words or ideas).

In particular, sources are required for material that is challenged or likely to be challenged – if reliable sources cannot be found for challenged material, it is likely to be removed from the article. Sources are also required when quoting someone, with or without quotation marks, or closely paraphasing a source. However, the citing of sources is not limited to those situations – editors are always encouraged to add or improve citations for any information contained in an article.

Citations are especially desirable for statements about living persons, particularly when the statements are contentious or potentially defamatory. In accordance with the biography of living persons policy, unsourced information of this type is likely to be removed on sight.

Citations are not used on disambiguation pages (sourcing for the information given there should be done in the target articles). Citations are also often discouraged in the lead section of an article, insofar as it summarizes information for which sources are given later in the article, although such things as quotations and particularly controversial statements should be supported by citations even in the lead.

For an image or other media file, details of its origin and copyright status should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself, or for text that merely identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg).

Inline citations

Shortcut: WP:INCITE

Further information: Wikipedia:Inline citation

Inline citations allow the reader to associate a given bit of material in an article with the specific reliable source(s) that support the material. Inline citations are most commonly added using either footnotes (long or short) or parenthetical references. This section describes how to add either type, and also describes how to create a list of full bibliography citations to support shortened footnotes or parenthetical references.

Footnotes

How to place an inline citation using ref tags

Shortcut: WP:CITEFOOT

To create a footnote, use the <ref>...</ref> syntax at the appropriate place in the article text, for example:

Justice is a human invention.<ref>Rawls, John. ''A Theory of Justice''. Harvard University Press, 1971, p. 1.</ref> It...

which will be displayed as something like:

Justice is a human invention. It...

It will also be necessary to generate the list of footnotes (where the citation text is actually displayed); for this, see the next section.

As in the above example, citation markers are normally placed after adjacent punctuation such as periods and commas. For exceptions, see the Punctuation and footnotes section of the Manual of Style. Note also that no space is added before the citation marker.

The citation should be added close to the material it supports, offering text-source integrity. If a word or phrase is particularly contentious, an inline citation may be added next to that word or phrase within the sentence, but it is usually sufficient to add the citation to the end of the sentence or paragraph, so long as it's clear which source supports which part of the text. If an infobox or table contains text that needs citing, but the box or table cannot incorporate an inline citation, the citation should appear in a caption or other text that discusses the material.

How to create the list of citations

The first editor to add footnotes to an article must create a section where the text of those citations appears. This section is placed at or near the bottom of the article and is usually titled "Notes" or "References." For more about the order and titles of sections at the end of an article (which may also include "Further reading" and "External links" sections), see Wikipedia:Footers.

Shortcut: WP:ASL

With some exceptions discussed below, citations appear in a single section containing only the <references /> tag or the {{reflist}} template. For example:

==Notes==

{{reflist}}

The footnotes will then automatically be listed under that section heading. Each numbered footnote marker in the text is a clickable link to the corresponding footnote, and each footnote contains a caret which links back to the corresponding point in the text. Scrolling lists, or lists of citations appearing within a scroll box, should never be used. This is because of issues with readability, browser compatibility, accessibility, printing, and site mirroring.

If an article contains a list of general references, this is placed in a separate section, titled (for example) "References". This usually comes immediately after the section(s) listing footnotes, if any. (If the general references section is called "References", then the citations section is usually called "Notes".)

Separating citations from explanatory footnotes

If an article contains both footnoted citations and other (explanatory) footnotes, then it is possible (but not necessary) to divide them into two separate lists, using the grouping feature described in the Grouping footnotes section of the footnotes help page. The explanatory footnotes and the citations are then placed in separate sections, called (for example) "Notes" and "References" respectively.

Repeated citations

For multiple use of the same citation or footnote, you can also use the named references feature, choosing a name to identify the citation, and typing <ref name="name">text of the citation</ref>. Thereafter, the same footnote may be reused any number of times by typing just <ref name="name" />. For more details of this syntax, see Multiple references to the same footnote on the footnotes help page.

Avoiding clutter

Inline references can significantly bloat the wikitext in the edit window and can be extremely difficult and confusing. There are three methods that avoid clutter in the edit window: list-defined references, short citations or parenthetical references. (As with other citation formats, articles should not undergo large scale conversion between formats without consensus to do so.)

Citing multiple pages of the same source

When an article cites many different pages from the same source, most Wikipedia editors use short citations in footnotes. Other methods include short citations in parenthesis and the template {{rp}}.

Shortcut: WP:IBID

The use of ibid., Id. (or similar abbreviations) is discouraged, as these may become broken as new references are added (op. cit. is less problematic in that it should refer explicitly to a citation contained in the article; however, not all readers are familiar with the meaning of the terms). If the use of ibid is extensive, use the {{ibid}} template.

Short citations

Shortcuts: WP:CITESHORT WP:SFN

Main page: Help:Shortened footnotes

Some Wikipedia articles use short citations, giving summary information about the source together with a page number, as in <ref>Smith 2010, p. 1.</ref>. These are used together with general references, which give full details of the sources, but without page numbers, and are listed in a separate "References" section. Short citations are used in articles which apply parenthetical referencing (see below), but they can also be used as footnote citations, as described here.

Forms of short citations used include author-date referencing (APA style, Harvard style, or Chicago style), and author-title or author-page referencing (MLA style or Chicago style). As before, the list of footnotes is automatically generated in a "Notes" or "Footnotes" section, which immediately precedes the "References" section containing the general references. Short citations can be written manually, or by using the {{sfn}} or {{harvnb}} templates. (Note that templates should not be added without consensus to an article that already uses a consistent referencing style.) The short citations and general references may be linked so that the reader can click on the short note to find full information about the source. See the template documentation for details and solutions to common problems. For variations with and without templates, see wikilinks to full references. For a set of realistic examples, see these.

This is how short citations look in the edit box:

The Sun is pretty big,<ref>Miller 2005, p. 23.</ref> but the Moon is not so big.<ref>Brown 2006, p. 46.</ref> The Sun is also quite hot.<ref>Miller 2005, p. 34.</ref> == Notes == {{Reflist}} == References == *Brown, Rebecca (2006). "Size of the Moon," ''Scientific American'', 51(78). *Miller, Edward (2005). ''The Sun''. Academic Press.

This is how they look in the article:

The Sun is pretty big, but the Moon is not so big. The Sun is also quite hot.

Notes

^ Miller 2005, p. 23.

^ Brown 2006, p. 46.

^ Miller 2005, p. 34.

References

Brown, Rebecca (2006). "Size of the Moon", Scientific American, 51(78).

Miller, Edward (2005). The Sun. Academic Press.

Shortened notes using titles rather than publication dates would look like this in the article:

Notes

^ Miller, The Sun, p. 23.

^ Brown, "Size of the Moon", p. 46.

^ Miller, The Sun, p. 34.

When using manual links it is easy to introduce errors such as duplicate anchors and unused references. The script User:Ucucha/HarvErrors will show many related errors. Duplicate anchors may be found by using the W3C Markup Validation Service.

Parenthetical referencing

Further information: Wikipedia:Parenthetical referencing

While most articles use footnote citations as described in the above sections, some articles use a parenthetical referencing style. Here, short citations in parentheses, such as (Smith 2010, p. 1), are placed within the article text itself. Full details of each source used are given in a general reference, e.g. Smith, John. Name of Book. Cambridge University Press, 2010. The general references are listed in alphabetical order, according to the authors' surnames, at the end of the article in a "References" section.

Several forms of short citation are used in Wikipedia; see Short citations above. The inline citation and general reference may be linked using a template (see linking inline and full citations); as with other citation templates, these should not be added to articles without consensus.

This is how it looks in the edit box:

The Sun is pretty big (Miller 2005, p. 1), but the Moon is not so big (Brown 2006, p. 2). The Sun is also quite hot (Miller 2005, p. 3). == References == *Brown, R (2006). "Size of the Moon", ''Scientific American'', 51(78). *Miller, E (2005). ''The Sun'', Academic Press.

This is how it looks in the article:

The Sun is pretty big (Miller 2005, p. 1), but the Moon is not so big (Brown 2006, p. 2). The Sun is also quite hot (Miller 2005, p. 3).

References

Brown, R (2006). "Size of the Moon", Scientific American, 51(78).

Miller, E (2005). The Sun, Academic Press.

Notice that, unlike footnotes, parenthetical references are placed before adjacent punctuation such as commas and full stops.

General references

Shortcut: WP:GENREF

A general reference is a citation to a reliable source that supports content, but is not displayed as an inline citation. General references are usually listed at the end of the article in a "References" section, and are usually sorted by the last name of the author or the editor. Examples of general reference sections are given above, in the sections on short citations and parenthetical references.

In addition to their use when short or parenthetical references are used, a general references section may also be included in an article that uses full inline citations, particularly if such citations have not yet been given for all the information in the article. In underdeveloped articles, a general references section may exist even though no inline citations at all have yet been added, especially when all article content is supported by a single source. The disadvantage of using general references alone is that text-source integrity is lost, unless the article is very short.

What information to include

Shortcut: WP:CITEHOW

Listed below is the information which a typical inline citation or general reference will provide, in order to identify the source, assist readers in finding it, and (in the case of inline citations) indicate the place in the source where the information is to be found. (If an article uses parenthetical referencing or short citations, then the inline citations will refer to this information in abbreviated form, as described in the relevant sections above.)

Books

Shortcuts: WP:EBOOK WP:BOOKLINKS

Citations for books typically include the name of the author(s), the title of the book (in italics), the volume if applicable, the city of publication (optional), the name of the publisher, the year of publication, and the ISBN number (optional), written using the syntax described at WP:ISBN.

Inline citations should additionally give the relevant page number or range of page numbers. Chapter numbers can also be given if appropriate. When specifying a page number, it is helpful to specify the date and edition used, as pagination can change between editions. If the source is an e-book that does not provide page numbers, the citation should include information that enables readers to locate the source material within the e-book, such as chapter number, paragraph number, or a short quote from the source itself.

Citations for individually authored chapters in books typically include the name of the author, the title of the chapter, the name of the book's editor, name of book, publisher, and year. Do not present the information in a way that implies the editor is the author.

When a book is available online through a site such as Internet Archive, Project Gutenberg, Biodiversity Heritage Library, or Google Books, it may be useful to provide a link to the book so readers can view the source. Use the external link syntax, so that clicking on the book title will take the reader to the book. If a specific page in the book is referenced, it may be specified in the link, for example

Rawls, John. [http://books.google.com/books?id=kvpby7HtAe0C&pg=PA18 ''A Theory of Justice'']. Harvard University Press, 1971, p. 18.

A link to a specific page in a Google Books should only be added if the book is available for preview; such links will not work if the book is only available in snippet view. Like other variations on citation styles, there is no requirement either to add or remove such links.

Journal articles

Citations for journal articles typically include the name of the author(s), the year and sometimes month of publication, the title of the article (within quotation marks), the name of the journal (in italics), the volume number, issue number and page numbers (article numbers in some electronic journals). It is also helpful to provide DOI, PMID and/or other identifiers where available. Because the Wikipedia is not an academic text, it is better to cite the title of the journal in full, rather than with an academic abbreviation.

Inline citations usually also include specific page numbers, as described above for books.

If the article is available online, use external link or URL syntax to link the article title to the relevant Web page, for example: Carr A, Ory D (2006). [http://dx.doi.org/10.1371/journal.pmed.0030496 Does HIV cause cardiovascular disease?] ''PLoS Medicine'', 3(11):e496.

Newspaper articles

Citations for newspaper articles typically include the name of the newspaper (in italics), the date of publication, the byline (author's name) if any, the title of the article (within quotation marks), and the city of publication if not included in the name of the newspaper. Page number(s) are optional.

If the article is available online, link the article's title to the relevant Web address, as described above for journal articles.

Web pages

Citations for World Wide Web pages typically include the name of the author(s) (if known), the title of the article (within quotation marks), the name of the website, the date of publication (if known), the date you retrieved the page, for example 'Retrieved 15 July 2008' or 'Retrieved 2008-07-15' (this is required if the publication date is unknown). Page number(s), section headings, or other location identifiers may be added if applicable.

Recordings

Citations for sound recordings typically include the name of the composer(s)/script writer(s), name of the performer(s), title of the song or individual track (in quotation marks), title of the album in italics (if applicable), name of the record label, year of release, medium (for example: LP, audio cassette, CD, MP3 file).

Citations for films, TV episodes, or video recordings typically include the name of the director (and the producer if relevant), names of major performers, the title of the episode in quotation marks (if applicable), the title of the film or TV series (in italics), the name of the studio, the year of release, the medium (for example: film, videocassette, DVD).

Where applicable, an inline citation should also give the approximate time in the recording at which the event or point of interest occurs. When doing this, be as precise as possible about the version of the source that you are citing; for example, movies are often released in different editions or "cuts", and timings may differ between them.

Say where you read it

Shortcut: WP:SAYWHEREYOUGOTIT

Don't cite a source unless you've seen it for yourself. Where you want to cite John Smith, but you've only read Paul Jones who cites Smith, write it like this (this formatting is just an example):

Smith, John. Name of Book I Haven't Seen, Cambridge University Press, 2009, p. 1, cited in Paul Jones (ed.). Name of Encyclopedia I Have Seen. Oxford University Press, 2010, p. 2.

However, if you have read Smith's book yourself, you may cite it directly; there is no need to give credit to any sources, search engines, websites, library catalogs, etc., that led you to that book.

Additional annotation

In most cases it is sufficient for a citation footnote simply to identify the source (as described in the sections above); readers can then consult the source to see how it supports the information in the article. Sometimes, however, it is useful to include additional annotation in the footnote, for example to indicate precisely which information the source is supporting (particularly when a single footnote lists more than one source – see Bundling citations and Text-source integrity below). A footnote may also contain a relevant exact quotation from the source, if this may be of interest (this is particularly useful if the source is not easily accessible).

In the case of non-English sources, it may be helpful to quote from the original text and then give an English translation. If the article itself contains a translation of a quote from such a source (without the original), then the original should be included in the footnote. See Non-English sources in the verifiability policy for more information.

Citation style

This section is the subject of a current discussion on the talk page.
Please feel free to join in. This doesn't mean that you may not be bold in editing this section, but it can't hurt to check the discussion first.

While citations should aim to provide the information listed above, there is no one single style for doing this, in terms of ordering of the information, punctuation, etc. A consistent style should be used within any given article, but it is not necessary to maintain consistency between articles – for how to deal with variation, see the following section.

A number of citation styles exist (some relevant Wikipedia articles include Citation, APA style, MLA style, The Chicago Manual of Style, Author-date referencing, Vancouver system and Bluebook). Examples can be found at Wikipedia:Citing sources/Example style.

Although nearly any consistent style may be used, avoid all-numeric date formats other than YYYY-MM-DD, because of the ambiguity concerning which number is the month and which the day. For example, 2002-06-11 may be used, but not 11/06/2002. The YYYY-MM-DD format should in any case be limited to Gregorian calendar dates where the year is after 1582.

Variation in citation methods

Shortcut: WP:CITEVAR

As described in various sections of this page, different articles use different citation systems, styles and methods. Points of difference include:

whether an article uses full citations, short citations in footnotes, or parenthetical referencing;
what the citation/reference sections of the article are called, and whether explanatory footnotes are grouped separately from citation footnotes;
the styling of the citations themselves;
whether citations are produced using citation templates;
whether list-defined references are used.

On all of these points, Wikipedia does not have a single house style. Editors may choose any option they want; one article need not match what is done in other articles or what is done in professional publications or recommended by academic style guides. However, citations within a given article should follow a consistent style.

It is therefore considered helpful:

when adding citations, to try to follow the system and style already in use in the article (if any);
to improve existing citations by adding missing information (for example, replacing bare URLs with full bibliographic citations);
to replace (or supplement) some or all general references with inline citations;
to change existing citations to make them follow a consistent system and style, if there is currently inconsistency within the article. If there is disagreement about which style is best, defer to the style used by the first major contributor or start a discussion on the talk page;

Editors should not attempt to change an article's established citation style merely on the grounds of personal preference, or without first seeking consensus for the change. If you think another system or style would be more appropriate for the article than what is already in use, then propose the change on the talk page, and wait for consensus to emerge.

Handling links in citations

As noted above under What information to include, it is helpful to include hyperlinks to source material, when available. Here we note some issues concerning these links.

Avoid embedded links

Further information: Wikipedia:Embedded citations

Embedded links to external websites should not be used as a form of inline citation, because they are highly susceptible to linkrot. Wikipedia allowed this in its early years—for example by adding a link after a sentence, like this [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html], which looks like this. [1] This is no longer recommended. Raw links are not recommended in lieu of properly written out citations, even if placed between ref tags, like this <ref>[http://media.guardian.co.uk/site/story/0,14173,1601858,00.html]</ref>.

Embedded links should never be used to place external links in the body of an article, like this: "Apple, Inc. announced their latest product..."

Convenience links

Main page: Wikipedia:Copyrights#Linking to copyrighted works

A convenience link is a link to a copy of your source on a webpage provided by someone other than the original publisher or author. For example, a copy of a newspaper article no longer available on the newspaper's website may be hosted elsewhere. When offering convenience links, it is important to be reasonably certain that the convenience copy is a true copy of the original, without any changes or inappropriate commentary, and that it does not infringe the original publisher's copyright. Accuracy can be assumed when the hosting website appears reliable. Where several sites host a copy of the material, the site selected as the convenience link should be the one whose general content appears most in line with Wikipedia:Neutral point of view and Wikipedia:Verifiability.

Indicating availability

If your source is not available online, it should be available in reputable libraries, archives, or collections. If a citation without an external link is challenged as unavailable, any of the following is sufficient to show the material to be reasonably available (though not necessarily reliable): providing an ISBN or OCLC number; linking to an established Wikipedia article about the source (the work, its author, or its publisher); or directly quoting the material on the talk page, briefly and in context.

Links to sources

For a source available in hardcopy, microform, and/or online, omit, in most cases, which one you read. While it is useful to cite author, title, edition (1st, 2nd, etc.), and similar information, it generally is not important to cite a database such as ProQuest, EbscoHost, or JStor (see the list of academic databases and search engines) or to link to such a database requiring a subscription or a third party's login. The basic bibliographic information you provide should be enough to search for the source in any of these databases that have the source. Don't add a URL that has a part of a password embedded in the URL. However, you may provide the DOI, ISBN, or another uniform identifier, if available. If the publisher offers a link to the source or its abstract that does not require a payment or a third party's login for access, you may provide the URL for that link. And if the source only exists online, give the link even if access is restricted.

Preventing and repairing dead links

Text-source integrity

Shortcut: WP:INTEGRITY

When using inline citations, it is important to maintain text-source integrity. The point of an inline citation is to allow readers and other editors to check that the material is sourced; that point is lost if the citation is not clearly placed. The distance between material and its source is a matter of editorial judgment, but adding text without placing its source clearly can lead to allegations of original research, violations of the sourcing policy, and even plagiarism. Editors should exercise caution when rearranging or inserting material to ensure that text-source relationships are maintained.

When new text is inserted into a paragraph make sure that it is clear what facts the inline citations support. For example

The sun is pretty big. The sun is also quite hot.

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Do not add facts into a fully cited paragraph or sentence

N The sun is pretty big, but the moon is not so big. The sun is also quite hot.

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

without including a source to cover the new information.

Y The sun is pretty big, but the moon is not so big. The sun is also quite hot.

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Brown, Rebecca. "Size of the Moon," Scientific American, 51(78):46.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Including too many citations within a sentence may be aesthetically unpleasant:

The sun is the closest star to the planet Earth, but the moon is even closer.

So consider placing them at a more aesthetically pleasant location:

The sun is the closest star to the planet Earth, but the moon is even closer.

However this solution brings its own problems:

A string of independent citations can also appear aesthetically unpleasant so consider bundling them into one.
Identifying which inline citation supports which fact can be more difficult unless additional information is added to the inline citations to explicitly identify what portion of the sentence they cover.
Maintenance becomes more difficult. When adding more information to the sentence from yet another source it may be difficult to work out precisely where to place the new citation. If the text is rearranged during a copy edit greater care needs to be taken with rearranging the citations, particularly as the inline citations will be renumbered during their repositioning.

For example if the sentence

The sun is the closest star to the planet Earth, but the moon is even closer.

is rearranged like this:

The moon is closer to planet Earth than the nearest star which is called the sun.

It will be fairly easy to check that the citations support the information in the rearranged sentence. This rearrangement is more difficult to check:

The sun is the closest star to the planet Earth, but the moon is even closer.

The moon is closer to planet Earth than the nearest star which is called the sun.

Bundling citations

Shortcuts: WP:CITEBUNDLE WP:BUNDLING

Further information: Wikipedia:Citation overkill

Sometimes the article is more readable if multiple citations are bundled into a single footnote. For example, when there are multiple sources for a given sentence, and each source applies to the entire sentence, the sources can be placed at the end of the sentence, like this. Or they can be bundled into one footnote at the end of the sentence or paragraph, like this.

Bundling is useful if the sources each support a different portion of the preceding text, or if the sources all support the same text. Bundling has several advantages:

It helps readers and other editors see at a glance which source supports which point, maintaining text-source integrity;
It avoids the visual clutter of multiple clickable footnotes inside a sentence or paragraph;
It avoids the confusion of having multiple sources listed separately after sentences, with no indication of which source to check for each part of the text, such as this.
It makes it less likely that inline citations will be moved inadvertently when text is re-arranged, because the footnote states clearly which source supports which point.

When formatting multiple citations in a footnote, there are several layouts available, as illustrated below. Within a given article, only a single layout should be used.

The sun is pretty big, but the moon is not so big. The sun is also quite hot.

Notes

Bullets

^ For the sun's size, see Miller, Edward. The Sun. Academic Press, 2005, p. 1.

For the moon's size, see Brown, Rebecca. "Size of the Moon," Scientific American, 51(78):46.

For the sun's heat, see Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Line breaks

^ For the sun's size, see Miller, Edward. The Sun. Academic Press, 2005, p. 1.
For the moon's size, see Brown, Rebecca. "Size of the Moon," Scientific American, 51(78):46.
For the sun's heat, see Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.
Paragraph

^ For the sun's size, see Miller, Edward. The Sun. Academic Press, 2005, p. 1. For the moon's size, see Brown, Rebecca. "Size of the Moon," Scientific American, 51(78):46. For the sun's heat, see Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

In-text attribution

Shortcut: WP:INTEXT

In-text attribution is the attribution inside a sentence of material to its source, in addition to an inline citation after the sentence. In-text attribution should be used with direct speech (a source's words between quotation marks); indirect speech (a source's words without quotation marks); and close paraphrasing. It can also be used when loosely summarizing a source's position in your own words. It avoids inadvertent plagiarism, and helps the reader see where a position is coming from. An inline citation should follow the attribution, usually at the end of the sentence or paragraph in question.

For example:

Y John Rawls argues that, to reach fair decisions, parties must consider matters as if behind a veil of ignorance.

When using in-text attribution, make sure it doesn't lead to an inadvertent neutrality violation. For example, the following implies parity between the sources, without making clear that the position of Dawkins is the majority view:

N Richard Dawkins argues that human beings evolved through natural selection, but John Smith writes that we arrived here in pods from Mars.

Neutrality issues apart, there are other ways in-text attribution can mislead. The sentence below suggests The New York Times has alone made this important discovery:

N According to The New York Times, the sun will set in the west this evening.

Simple facts such as this can have inline citations to reliable sources as an aid to the reader, but normally the text itself is best left as a plain statement without in-text attribution:

YBy mass, oxygen is the third most abundant element in the universe after hydrogen and helium.

Dealing with unsourced material

Shortcut: WP:NOCITE

If an article is unreferenced, you can tag it with the {{unreferenced}} template, so long as it is not nonsensical or a biography of a living person, in which case request admin assistance.

If a claim is doubtful but not harmful, use the {{citation needed}} template, which will add an inline tag, but remember to go back and remove the claim if no source is produced within a reasonable time.
If a claim is doubtful and harmful, remove it from the article. You may want to move it to the talk page and ask for a source, unless it is very harmful or absurd, in which case it should not be posted to the talk page either. Use your common sense.
All unsourced and poorly sourced contentious material about living persons must be removed from articles and talk pages immediately. See Wikipedia:Biographies of living persons and Wikipedia:Libel.

Citation templates and tools

Further information: Wikipedia:Citation templates and Wikipedia:Citation tools

For a comparison of citations using templates with citations written freehand, see Wikipedia:Citing sources/Example edits for different methods.

Citation templates can be used to format citations in a consistent way. The use of citation templates is neither encouraged nor discouraged: an article should not be switched between templated and non-templated citations without good reason and consensus – see Variation in citation methods above.

If citation templates are used in an article, the parameters should be accurate. It is inappropriate to set parameters to false values in order that the template will be rendered to the reader as if it were written in some style other than the style normally produced the template (e.g. MLA style).

Metadata

Citations may be accompanied by metadata, though it is not mandatory. Most citation templates on Wikipedia use the COinS standard. Metadata such as this allow browser plugins and other automated software to make citation data accessible to the user, for instance by providing links to their library's online copies of the cited works. In articles that format citations manually, metadata may be added manually in a span, according to the COinS specification.

Citation processing tools

Citation template generator – generates completed templates using identifying numbers such PMIDs (PubMed IDs).
Template:Citation/core – a core template used by other citation templates
User:Citation bot (formerly DOI bot) – a bot that automatically fixes common errors in individual citations, and adds missing fields
User:CitationTool – a tool for finding article-level citation errors and fixing them. Not currently functional.
Wikipedia citation tool for Google Books – converts bare Google book links into {{cite book}} format.
DOI Wikipedia reference generator
New York Times Wikipedia reference generator
Reflinks adds titles to bare references and other cleanup

Programming tools

Wikicite is a free program that helps editors to create citations for their Wikipedia contributions using citation templates. It is written in Visual Basic .NET, making it suitable only for users with the .NET Framework installed on Windows, or, for other platforms, the Mono alternative framework. Wikicite and its source code is freely available; see the developer's page for further details.
- Wikicite+ is a program based on the original Wikicite source code. It features extra validation, bug fixes, additional cite templates (such as cite episode) as well as tools for stub sorting and more. It is also available for free under the Apache License 2.0 and is open source.
User:Richiez has tools to automatically handle citations for a whole article at a time. Converts occurrences of {{pmid XXXX}} or {{isbn XXXX}} to properly formatted footnote or Harvard-style references. Written in ruby and requires a working installation with basic libraries.
pubmed2wiki.xsl an XSL stylesheet transforming the XML output of PubMed to Wikipedia refs.
RefTag by Apoc2400 creates a prefilled {{cite book}} template with various options from a Google Books URL. The page provides a bookmarklet for single-click transfer.
wikiciter web interface, does google books, pdf files, beta.

Citation export tools

You can insert a link beside each citation in Wikipedia, allowing you to export the citation to a reference manager such as EndNote. To install the script just add the following line to Special:MyPage/skin.js (applies to the currently selected skin) or Special:MyPage/common.js (applies to all skins)"

importScript("User:Smith609/endnote.js");

Then save the page and follow the instructions at the top of that page to bypass your browser's cache.

Notes

^ See this July 2007 discussion for more detail on why scrolling reference lists should not be used.
^ The {{Cite book}} template can be used to pinpoint the source material within an e-book, by utilizing one or more of the following parameters:
- |type= to indicate the e-book device and version; example: |type=Kindle 3
- |at= to indicate the location; example: |at=Location 4337-42
- |at= to indicate the chapter, section and/or paragraph; example: |at=chapter 1, section 2, para. 3.
- |quote= to include a short, relevant quote.
^ See the October 2010 RfC on linking to Google Books.

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