Wikipedia:Citing sources

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

This page in a nutshell: This guideline discusses how to format citations. For the policy on sourcing, see Verifiability.

A citation is a line of text that uniquely identifies a source. For example:

Ritter, Ron. The Oxford Style Manual. Oxford University Press, 2002, p. 1.

When to cite sources: The policy on sourcing is Verifiability, which requires inline citations for any material challenged or likely to be challenged, and for all quotations. The policy is strictly applied to all material in the mainspace—articles, lists, captions, and sections of articles—without exception. In the event of a contradiction between this page and the policy, the policy takes priority, and this page should be updated to reflect it. Sourcing also applies to images: when an image is uploaded, the uploader must say where the image came from and indicate its copyright status.

How to write 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 is that you provide enough information to identify the source, and others will improve the formatting if needed.

Background

Use of terms

Source, reference, citation

The word "source" has three meanings on Wikipedia: the piece of work itself, the creator of the work, and the publisher of the work.^[1] A "citation" is a line of text that identifies a source. The word "reference" may refer to the citation or the source. The most common citation system on Wikipedia is a footnote system. The terms "footnote" and "note" are used interchangeably, and there is no separate use of the term "endnote." The terms "Further reading" and "External links" are used as section headings for texts that may be of interest but have not been used as sources.

Inline citations

An inline citation is a citation next to the material it supports. Inline citations help to maintain text-source integrity. If the material is particularly contentious, an inline citation may be added within a sentence, but adding it to the end of the sentence or paragraph is usually sufficient. The two styles of inline citation on Wikipedia are clickable footnotes (<ref> tags) and parenthetical references.

When and why to cite sources

• Cite sources when:

• adding or restoring material that is challenged or likely to be challenged
• quoting someone
• uploading an image

• Citing sources:

• ensures that content can be checked by any reader or editor
• shows that your edit is not original research
• ensures that material about living persons complies with the biography of living persons policy
• avoids claims of plagiarism and copyright violation
• helps users find additional information
• improves the credibility of Wikipedia

Dealing with unsourced material

If an article is unreferenced you can tag it with the template {{Unreferenced}}, 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 {{fact}} tag, which will add "citation needed," 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.

How to format inline citations

Editors are free to use any method for inline citations; no method is preferred over another.

A quick how-to

Most editors use footnotes. One easy way to write them is to add this to the end of the relevant sentence or paragraph:

• <ref>Smith, Jane. ''Name of Book''. Cambridge University Press, 2010. p. 1.</ref>
• <ref>Sanger, David E. [http://www.nytimes.com/2010/09/24/world/24prexy.html?_r=1&hp "With Warning, Obama Presses China on Currency"], ''The New York Times'', September 23, 2010, accessed October 31, 2010.</ref>

Then add this to the end of the article:

==Notes==
{{reflist}}

See below for more details.

Footnotes

How to write them

Most Wikipedia articles place their citations in footnotes. These appear as clickable numbers within the text, which link to a numbered list of full citations at the end of the article. The citations will appear at the end of the article if you type {{reflist}}.^[2] This will generate the list of footnotes. This is usually called the Notes or References section.

For a citation to appear in a footnote, it must be enclosed within"ref" tags. You can add these by typing <ref> at the front of the citation and </ref> at the end. Alternatively use the list of "markup" in the edit box, which includes <ref></ref>. You can also use the name attribute by using <ref name="name">details of the citation</ref>. Thereafter, the same footnote may be used multiple times by adding <ref name=name/>. If you use more than one word, you have to add straight quotation marks (<ref name="name and name"/>).

This is how it looks in the edit box:

The sun is pretty big,<ref>Miller, Edward. ''The Sun''. Academic Press, 2005, p. 1.</ref>
but the moon is not so big.<ref>Brown, Rebecca. "Size of the Moon," ''Scientific American'', 51(78):46.</ref>
The sun is also quite hot.<ref>Smith, John. ''The Sun's Heat''. Academic Press, 2005, p. 2.</ref>
==Notes==
<references />

This is how it looks in the article:

The sun is pretty big,^[1] but the moon is not so big.^[2] The sun is also quite hot.^[3]

Notes

---

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

Bundling citations

You can combine or "bundle" citations between one set of ref tags to avoid visual clutter. This can be done with long or short footnotes, with or without citation templates. If you bundle several citations, it is helpful to explain to the reader inside the footnote which citation supports which point in the text:

The sun is pretty big, but the moon is not so big. The sun is also quite hot.^[1]

Notes

---

1. ^ 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.

Shortened footnotes

Many articles use shortened citations in footnotes, giving the author, year, and the page number as appropriate, such as <ref>Smith, 2010, p. 1.</ref> As before, the list of footnotes is automatically generated in a "Notes" or "Footnotes" section. A full citation is then added in a "References" section.

Short citations can be written manually, or by using the {{sfn}} or {{harvnb}} templates, though note that templates should not be added without consensus to an article that already uses a consistent referencing style. If using templates, the short citation and the full citation may be linked so that the reader may click on the short note to highlight the full citation (see wikilinks to full references).

This is how it looks 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|2}}

== References ==
*Brown, Rebecca (2006). "Size of the Moon," ''Scientific American'', 51(78).
*Miller, Edward (2005). ''The Sun''. Academic Press.

This is how it looks in the article:

The sun is pretty big,^[1] but the moon is not so big.^[2] The sun is also quite hot.^[3]

Notes

---

1. ^ Miller 2005, p. 23.
2. ^ Brown 2006, p. 46.
3. ^ 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

---

1. ^ Miller, The Sun, p. 23.
2. ^ Brown, "Size of the Moon", p. 46.
3. ^ Miller, The Sun, p. 34.

For examples using shortened notes, see Wikipedia:Citing sources/Example edits for different methods.

List-defined references

As of September 2009, the Cite.php extension was modified to support list-defined references. These can be implemented with the |refs= parameter to the {{reflist}} template, or by using a pair of HTML tags (<references> and </references>) in place of the <references /> tag. These reduce clutter within articles, by putting all the citation details in the section at the end where the footnotes are displayed. As with other citation formats, these should not be added to articles that already have a stable referencing system, unless there is consensus to do so. When in doubt, use the referencing system added by the first major contributor to use a consistent style.

This is how it looks in the edit box::

The Sun is pretty big,<ref name="Miller2005p23" />
but the Moon is not so big.<ref name="Brown2006" />
The Sun is also quite hot.<ref name="Miller2005p34" />
==Notes==
{{reflist|refs=
<ref name="Miller2005p23">Miller, Edward.''The Sun''. Academic Press, 2005, p. 23.</ref>
<ref name="Miller2005p34">Miller, Edward.''The Sun''. Academic Press, 2005, p. 34.</ref>
<ref name="Brown2006">Brown, Rebecca. "Size of the Moon," ''Scientific American,'' 51(78):46</ref>
}}

This is how it looks in the article:

The Sun is pretty big,^[1] but the Moon is not so big.^[2] The Sun is also quite hot.^[3]

Notes

---

1. ^ Miller, Edward. The Sun. Academic Press, 2005, p. 23.
2. ^ Brown, Rebecca. "Size of the Moon," Scientific American, 51(78):46.
3. ^ Miller, Edward. The Sun. Academic Press, 2005, p. 34.

Defined references must be used within the body; unused references will show an error message. Non-list-defined references (ordinary footnote references enclosed with <ref> and </ref> tags) will display as normal along with list-defined ones.

Parenthetical referencing

Many forms of parenthetical referencing are used in Wikipedia, including author-date referencing (APA style, Harvard style, or Chicago style), and author-title or author-page referencing (MLA style or Chicago style). See Pros & Cons.

In parenthetical citations, a short version of the citation is added in parentheses just after the point it is supporting, comprising only the surname of the author(s) and the year of publication, and possibly page numbers (APA style); or the surname of the author(s) and possibly short titles and/or page numbers (MLA style).

Using author-date parenthetical references, the inline citation usually looks like: (Author 2006:28) or (Author 2006, p. 28). The full citation is then added at the end of the article to a "References" section. This list of full citations is usually ordered alphabetically by author name. As with shortened notes, the inline citation and the full citation may be linked so that the reader may click on the inline citation to highlight the full citation (see linking inline and full citations).

This is how it looks in the edit box:

The Sun is pretty big (Miller 2005),
but the Moon is not so big (Brown 2006, p. 46).
The Sun is also quite hot (Miller 2005, p. 34).
== 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), but the Moon is not so big (Brown 2006, p. 46). The Sun is also quite hot (Miller 2005, p. 34).

References

---

• Brown, R (2006). "Size of the Moon", Scientific American, 51(78).
• Miller, E (2005). The Sun, Academic Press.

Some general advice

Say where you read it

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; there are several ways this can be written):

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

Non-English sources

Because this is the English Wikipedia, English-language sources should be used in preference to non-English language sources of equal caliber and content, though the latter are allowed where appropriate. When quoting a source in a different language, please provide both the original-language quotation and an English translation, in the text, in a footnote, or on the talk page as appropriate.

Convenience links

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.

Multimedia

Multimedia material should be referenced just like article text. Citations for a media file should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. 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. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself. Material that identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg) is considered attribution and normally does not need further citation.

Avoid scrolling lists

Scrolling lists, or lists of citations appearing within a scroll box, should never be used because of issues with readability, accessibility, printing, and site mirroring. Additionally, it cannot be guaranteed that such lists will display properly in all web browsers. See this July 2007 discussion for more detail.

General reference

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. The disadvantage of using general references is that text-source integrity is lost, unless the article is very short. The sourcing policy, Verifiability, requires inline citations for all quotations, and for anything challenged or likely to be challenged.

A general reference is typically displayed like this:

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

Below is how this would look once the edit has been saved:

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

References

---

• Brown, R (2006). "Size of the Moon", Scientific American, 51(78).
• Miller, E (2005). The Sun, Academic Press.

Embedded links

Embedded links should not be used in place of footnotes. In its early years Wikipedia allowed this as a form of citation—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 permitted. Embedded links should also not be used to place external links to websites in the body of an article. For example, do not spam links to company websites in article text, like this: "Apple, Inc. announced their latest product..." InterWikimedia links may be appropriate in the body of an article; see Wikipedia:Wikimedia sister projects.

What information to include

Citation styles and consistency

There are a number of citation styles. See here for some examples. They all include the same information, but vary in punctuation and the order of the author's name, publication date, title, and page numbers. Citations in Wikipedia articles should be internally consistent. You should follow the style already established in an article if it has one; where there is disagreement, the style used by the first editor to use one should be respected.

Examples

Full citations for books typically include:

• name of the author(s)
• year of publication in brackets
• title of the book in italics
• volume when appropriate
• city of publication optional
• name of the publisher
• chapter or page number(s) where appropriate
• ISBN optional

Full citations for individually authored chapters in books additionally include:

• the book's overall editor
• the title of the chapter
• the chapter number or page numbers for the chapter

• see: Template:Citation

Full citations for journal articles typically include:

• name of the author(s)
• year and sometimes month of publication
• title of the article within quotation marks
• name of the journal in italics
• volume number, issue number (if the journal uses them), and page numbers (article numbers in some electronic journals)

Citations for newspaper articles typically include:

• name of the newspaper in italics (required)
• date of publication (required)
• byline (author's name), if any
• title of the article within quotation marks
• city of publication, if not included in name of newspaper
• page number(s) are optional

Citations for World Wide Web articles typically include:

• name of the author(s)
• title of the article within quotation marks
• name of the website (linked to a Wikipedia article about the site if it exists, or to Website's "about" page)
• date of publication
• page number(s) (if applicable)
• the date you retrieved it (required if the publication date is unknown)
• see: Template:Cite_web

Identifying parts of a source

When citing lengthy sources, you should normally identify which part of a source is being cited. For example, in the case of a book, specify the page number(s). Page numbers are especially important for lengthy, non-indexed books, but they are not required for a reference to the source as a whole, for example when describing a complete book or article or when the source is used to illustrate a particular point of view.

Whenever you specify a page number, it is helpful to specify the version (date and edition for books) of the source because the layout, pagination, length, etc. can change between editions.

Links and ID numbers

A citation ideally includes a link or ID number to help editors locate the source. If you have a URL (webpage) link, you can add it to the title part of the citation, so that when you add the citation to Wikipedia the URL becomes hidden and the title becomes clickable. To do this, enclose the URL and the title in square brackets—the URL first, then a space, then the title. 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.

For web-only sources with no publication date you should include a "Retrieved" date instead, in case the webpage changes in the future. For example: Retrieved 2008-07-15.

You can also add an ID number to the end of a citation. The ID number might be an ISBN for a book, a DOI (Digital Object Identifier) for an article, or any of several ID numbers that are specific to particular article databases, such as a PMID number for articles on PubMed. It may be possible to format these so that they are automatically activated and become clickable when added to Wikipedia, for example by typing ISBN (or PMID) following by a space followed by the ID number.

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.

Citation templates and tools

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

Citation templates are used to format citations in a consistent way. The use of citation templates is neither encouraged nor discouraged. Templates may be used or removed at the discretion of individual editors, subject to agreement with other editors on the article. Because templates can be contentious, editors should not change an article with a distinctive citation format to another without gaining consensus. Where no agreement can be reached, defer to the style used by the first major contributor.

There are several webpages/tools that can help quickly produce a citation in a standard template format. You may only need one piece of information and they can fill in the rest of the details. The resulting citation will be enclosed in "cite" tags, and it will be formatted in a particular way depending on which kind of template is being used. You can then copy all the text from there. It may still require additional tags before you can add it to a Wikipedia article.

Metadata

Citations may be accompanied by metadata, though it is not mandatory. Most citation templates on Wikipedia use the COinS microformat. 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; or the templates Template:Citation metadata or Template:COinS can be used.

Citation processing tools

• Template:Citation/core – a core template used by other citation templates
• User:CitationTool – a tool for finding article-level citation errors and fixing them. Not currently functional.
• Citation bot (formerly DOI bot) – a bot that automatically fixes common errors in individual citations, and adds missing fields

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.
• pubmed2wiki.xsl a XSL stylesheet transforming the XML output of PubMed to Wikipedia refs.
• 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.
• 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. Just copy this code:

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

to the end of Special:MyPage/monobook.js. Then, save the page and bypass your browser's cache.

Preventing and repairing dead links

To help prevent dead links, persistent identifiers are available for some sources. Some journal articles have a digital object identifier (DOI); some online newspapers and blogs, and also Wikipedia, have permalinks that are stable. When permanent links aren't available, consider archiving the referenced document when writing the article; on-demand web archiving services such as WebCite (http://www.webcitation.org) are fairly easy to use (see pre-emptive archiving).

Dead links should be repaired or replaced if possible. In most cases one of the following approaches will give an acceptable alternative.

• First, check the link to confirm that it is dead. The site may have been temporarily down or have changed its linking structure. If the link has returned to service but has been labeled as a dead link, simply remove the labeling. See {{dead link}}.
• If the document is no longer available at the original website, there may be a copy of the referenced document at a web archiving service. If so, update the citation to include a link to the archived copy of the referenced document.
  • The Internet Archive (http://www.archive.org/) has literally billions of archived webpages. Note that there may be a delay of six months before a recent link shows up there. See also the article Wikipedia:Using the Wayback Machine.
  • WebCite is an "on-demand" archiving service (http://www.webcitation.org) that should also be checked.
  • UK Government Web Archive (http://www.nationalarchives.gov.uk/webarchive/), a project of The National Archives, preserves 1500 UK central government websites captured by the European Archive Foundation.^[3]
• If a good copy of the original document cannot be located, it may be possible to find a substitute. Enter key words or phrases or other content from the cited material into the referenced website's search engine, into a similar website's search engine, or into a general search engine such as Google. (A search engine may hold a cached version of the dead link for a short time, which can help find a substitute.) Or, browse the referenced document's website or similar websites. If you find a new document that can serve as a substitute, update the dead link to refer to the new document.
• Deactivate the dead link, and keep the citation information if still appropriate to the article. (This may happen, for example, when an online copy of material that originally appeared in print is no longer online.) In the remaining citation, note that the dead link was found to be inactive on today's date. Even with an inactive link, the citation still records a source that was used, and provides a context for understanding archiving delays or for taking other actions. In order to deactivate the dead link, do one of the following.
  • Turn the dead link into plain text. Remove only enough of the dead link's wikitext or markup language or URI scheme (square brackets, "http://", and so on) so that clicking on the link does not take you to its destination. This will make the link visible to both readers and editors of the article.
  • Turn the dead link into an HTML comment. Place HTML comment markup language around the link. This will make the link disappear when reading the article, but will preserve the link for editors of the article.

If a dead link cannot be repaired or replaced, one option to consider is reworking the article section so that it no longer relies on the dead link or is supported by an alternative source, though this is not required. Regardless of whether a dead link can or cannot be repaired or replaced, remember that Wikipedia policy (including policy on sources and biographies of living persons) still applies.

Also, do not delete article assertions solely because the URL of an online supporting source does not work any longer. WP:Verifiability does not require that all information be supported by a working link, nor does it require the source to be published on-line.

See also

Notes

References

Further reading