Wikipedia:Citing sources

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This page is considered a guideline on Wikipedia. It is generally accepted among editors and is considered a standard that all users should follow. However, it is not set in stone and should be treated with common sense and the occasional exception. When editing this page, please ensure that your revision reflects consensus. When in doubt, discuss first on the talk page.
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This page in a nutshell: Include citations to reliable sources when you add content, especially regarding contentious issues and biographical material about living people.
Wikipedia policies
Article standards

Neutral point of view
Attribution
What Wikipedia is not
Biographies of living persons
Working with others

Civility
Consensus
No personal attacks
Resolving disputes

This page is a style guide, describing how to write citations in articles.

Wikipedia:Attribution, which is policy, mandates the provision of sources. Attribution is required for direct quotes and for material that is challenged or likely to be challenged. Any material that is challenged and for which no source is provided may be removed by any editor. For information about the importance of using good sources in biographies of living persons, see Wikipedia:Biographies of living persons, which is also policy.

If you don't know how to format the citation, provide as much information as you can, and others may fix it for you. Cite It!

Contents

Why sources should be cited

  • To credit a source for providing useful information and to avoid claims of plagiarism.
  • To show that your edit isn't original research.
  • To ensure that the content of articles is credible and can be checked by any reader or editor.
  • To help users find additional reliable information on the topic.
  • To improve the overall credibility and authoritative character of Wikipedia.
  • To reduce the likelihood of editorial disputes, or to resolve any that arise.
  • To ensure that material about living persons is reliably sourced and complies with Wikipedia:Biographies of living persons.

Note: Wikipedia articles and categories cannot be used as sources.

When to cite sources

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When you add content

All material that is challenged or likely to be challenged needs a source.

The need for citations is especially important when writing about opinions held on a particular issue. Avoid weasel words such as, "Some people say ..." Instead, make your writing verifiable: find a specific person or group who holds that opinion and give a citation to a reputable publication in which they express that opinion. Remember that Wikipedia is not a place for expressing your own opinions or for original research.

Because this is the English Wikipedia, English-language sources should be given whenever possible, and should always be used in preference to other language sources of equal calibre. However, do give references in other languages where appropriate. If quoting from a different language source, an English translation should be given with the original-language quote beside it.

When you verify content

You can add sources even for material you didn't write, by using a source to verify the material. Adding citations is an excellent way to contribute to Wikipedia. See Wikipedia:Forum for Encyclopedic Standards and Wikipedia:WikiProject Fact and Reference Check for organized efforts to add citations.

Material that is, or is likely to be, challenged

Think ahead. Try to imagine whether or not people might doubt what you wrote, or need more information about it. Supporting what is written in Wikipedia by referring to a clear and reliable source will add stability to your contribution.

Say where you got it

It is improper to copy a citation from an intermediate source without making clear that you saw only that intermediate source. For example, you might find some information on a web page which says it comes from a certain book. Unless you look at the book yourself to check that the information is there, your reference is really the web page, which is what you must cite. The credibility of your article rests on the credibility of the web page, as well as the book, and your article must make that clear.

When adding material to the biography of a living person

Main article: Wikipedia:Biographies of living persons

Biographies of living persons should be sourced with particular care, for legal and ethical reasons. All negative material about living persons must be sourced to a reliable source. Do not wait for another editor to request a source. If you find unsourced or poorly sourced negative material about a living person — whether in an article or on a talk page — remove it immediately! Do not leave it in the article and ask for a source. Do not move it to the talk page. This applies whether the material is in a biography or any other article.

When you quote someone

You should always add a citation when quoting published material, and the citation should be placed directly after the quotation, which should be enclosed within double quotation marks — "like this" — or single quotation marks if it's a quote-within-a-quote — "and here is such a 'quotation' as an example." For long quotes, you may wish to use Template:Quotation.

Shortcut:
WP:CITE#HOW

How to cite sources

Inline citations (references inserted into the text) may use one of the following three systems.

  1. Embedded HTML links
  2. Harvard referencing
  3. Footnotes (most often using <ref> and <references/> elements)
  • Follow the system used for an article's existing citations. Do not change formats without checking for objections on the talk page. If there is no agreement, prefer the style used by the first major contributor.
  • When sources are mentioned within the body of an article, it is helpful to identify them clearly on first reference. For example, this would mean including the first name and surname, that is, the full name the person usually uses. Even better is to include some information about the person's relevant background, such as, "John Smith, a history professor at Yale University, writes that ..."
  • If you are unclear as to which system or style to use, remember: the most important thing is to provide all the information one would need to identify and find the source. If necessary, put this information on the talk page, or in a comment on the main page, and ask others how to format it correctly for that article.

Citation templates

For transcluded templates, see Help:Template.

The use of citation templates is neither encouraged nor discouraged by this or any other guideline. Templates may be used at the discretion of individual editors, subject to agreement with the other editors on the article.

Some editors find them helpful, arguing that they maintain a consistent and accurate style across articles, while other editors find them annoying, particularly when used inline in the text, because they make the text harder to read in edit mode and therefore harder to edit. Some templates (such as {{cite book}} and {{cite journal}}) now also include machine-readable COinS tags.

Because they are optional, editors should not add templates without consensus.

Embedded HTML links

For more details on this topic, see Wikipedia:Embedded citations.

Web pages referenced in an article can be linked to directly by enclosing the URL in square brackets. For example, a reference to a newspaper article can be embedded like: [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html], which looks like this: [1]

A full citation is also required in the References section.

*Plunkett, John. [http://media.guardian.co.uk/site/story/0,14173,1601858,00.html "Sorrell accuses Murdoch of panic buying"], ''The Guardian'', October 27, 2005. Accessed October 27, 2005.

which appears as:

Harvard referencing

For more details on this topic, see Wikipedia:Harvard referencing.

Under the Harvard referencing system, a book is cited in the text in parentheses, after the section, sentence, or paragraph for which the book was used as a source, using the surname of the author and the year of publication only, with the parentheses closing before the period, as in (Author 2005). A full citation is then placed at the end of the text in an alphabetized list of "References". According to The Oxford Style Manual, the Harvard system is the "most commonly used reference method in the physical and social sciences" (Ritter 2002).

Page numbers must be included in a citation that accompanies a specific quotation from, or a paraphrase or reference to, a specific passage of a book or article.

In article, common variations:

  • For two authors, use (Smith & Jones 2005); for more authors, use (Smith et al. 2005).
  • If the same author has published two books in 2005, and both are being referenced in the text, this is written as (Author 2005a) and (Author 2005b).
  • The specific page, section, or division of the cited work can follow the date in this way: (Author 2006:28).
  • If the date of publication is unavailable, use "n.d." (meaning, no date)
  • Newspaper articles may give the name of the newspaper and the date of publication after the sentence (The Guardian, December 17, 2005).

In References:

For an article: in the case of (Traynor 2005) or (The Guardian, December 17, 2005), this might be:

Note: Harvard referencing is not complete without the full citation at the end of the page (article) in the References section, as described below.

Footnotes

For more details on this topic, see Wikipedia:Footnotes.

A footnote is a note placed at the bottom of a page of a document to comment on a part of the main text, or to provide a reference for it, or both. The connection between the relevant text and its footnote is indicated by a number or symbol which appears both after the relevant text and before the footnote.

  1. Place a <ref> ... </ref> where you want a footnote reference number to appear in an article—type the text of the note between the ref tags.
  2. Place the <references/> tag in a "Notes" or "References" section near the end of the article—the list of notes will be generated here.

Example:

According to scientists, the Sun is pretty big,<ref>Miller, E: "The Sun", page 23. Academic Press, 2005</ref>
however the moon is not so big.<ref>Smith, R: "Size of the Moon", ''Scientific American'', 46(78):46</ref>

== References ==
<references/>

Result:

According to scientists, the Sun is pretty big,[1] however the moon is not so big.[2]

Footnotes come after punctuation

Some words, phrases or facts must be referenced mid-sentence; footnotes at the end of a sentence or phrase are placed immediately after the punctuation. For example: President Bush called for a halt to the violence,[3] and opposed a timetable for withdrawal.[4]

What footnotes are normally used for

  • Some publications use footnotes for both the full citation of a source, and for additional comments or information of interest to the reader.
  • Some publications use Harvard style notation for sources, and use footnotes exclusively for tangential comments or more detailed information. In this case, in other words, footnotes are notes with relevant text that would distract from the main point if embedded in the main text, yet are helpful in explaining a point in greater detail. Such footnotes can be especially helpful for later fact-checkers, to ensure that the article text is well-supported. Thus, using footnotes to provide useful clarifying information outside the main point is fine where this is needed.

Notes

footnote examples
  1. ^ Miller, E: "The Sun", page 23. Academic Press, 2005
  2. ^ Smith, R: "Size of the Moon", Scientific American, 46(78):46
  3. ^ example footnote abc
  4. ^ example footnote xyz

Full citations

All citation techniques require detailed full citations to be provided for each source used. They may be formatted by hand or using one of the citation templates.

Full citations typically include: the name of the author, the title of the book or article, and the date of publication. Page numbers are essential whenever possible. The name of the publisher and its city is optional. The ISBN of a book is optional. For journal articles, include volume number, issue number and page numbers. Citations for newspaper articles typically include the title of the article in quotes, the byline (author's name), the name of the newspaper in italics, date of publication, and the date you retrieved it if it is online.

For a book: in the case of two authors, this might be:

For an article: in the case of (Traynor 2005) or (The Guardian, December 17, 2005), this might be:

It is crucial that complete references be provided for each distinct edition referred to (or cited) in the article, and that each such in-line citation provide enough information to distinguish between editions.

Images

Images must include source details and a copyright tag on the image description page.

If you downloaded this image from the web, you should give the URL. Example:

Source: Downloaded from http://news.bbc.co.uk/1/hi/world/europe/4280841.stm

If you got the image from an offline source, you should specify. For example:

Source: Scanned from public record #5253 on file with Anytown, Somestate public surveyor

It is important that you list the author of the image (especially if different from the source), which is important both for copyright and for informational purposes. Some copyright licenses require that the original author receive credit for their work.

Notes

Recommended section names to use for footnotes in Wikipedia:

  • ==Notes== or
  • ==Footnotes== or
  • ==References==

Maintaining a separate "References" section in addition to "Notes"

It can be helpful when footnotes are used that a separate "References" section also be maintained, in which the sources that were used are listed in alphabetical order. With articles that have lots of footnotes, it can become hard to see after a while exactly which sources have been used, particularly when the footnotes also contain explanatory text. A References section, which lists citations in alphabetical order, helps readers to see at a glance the quality of the references used. Works cited in the References section may be cited in abbreviated short title form in specific footnotes, using the format <ref>Smith, Short Title, 182</ref>.

Further reading/External links

An ==External links== or ==Further reading== or ==Bibliography== section is placed near the end of an article and offers books, articles, and links to websites related to the topic that might be of interest to the reader. The section "Further reading" may include both online material and material not available online. If all recommended material is online, the section may be titled "External links". Some editors may include both headings in articles, listing only material not available online in the "Further reading" section.

All items used to verify information in the article must be listed in the "References" or "Notes" section, and are generally not included in "Further reading" or "External links". However, if an item used as a reference covers the topic beyond the scope of the article, and has significant usefulness beyond verification of the article, you may want to include it here as well. This also makes it easier for users to identify all the major recommended resources on a topic.

What to do when a reference link "goes dead"

See also: Wikipedia:Using the Wayback Machine, WebCite

When a link in the References section or Notes section (a link to a source for information in the article) "goes dead", it should be repaired or replaced if possible, but not deleted. External links/Further reading sections are not as important, but bad links in those sections should also be fixed. Often, a live substitute link can be found. In most cases, one of the following approaches will preserve an acceptable citation:

  • Some pages can be recovered from the Internet Archive or WebCite. Just go to http://www.archive.org/ or http://www.webcitation.org, respectively, and search for the old link by URL. Make sure that your new citation mentions the date the page was archived by the Internet Archive. In case of WebCite, any broken URL can be searched for and replaced using the format http://www.webcitation.org/query?url=URL&date=DATE, where URL is the URL that is broken and needs to be restored. The DATE variable is optional and indicates the (approximate) caching date. For example, http://www.webcitation.org/query?url=www.pewinternet.org/pdfs/PIP_Health_Report_July_2003.pdf&date=2005-12-31 retrieves a copy of the URL http://www.pewinternet.org/pdfs/PIP_Health_Report_July_2003.pdf which is closest to the date of Dec 31st, 2005 (in this example the actual caching date was 21 days before the requested date). WebCite allows on-demand prospective archiving and is not crawler-based, i.e. pages are only archived if the author has requested archiving when he cited the piece for the first time, which is highly recommended
  • If this was a non-blind citation of web-only material, it may be worth the effort to search the target site for an equivalent page at a new location, an indication that the whole site has moved, etc.
  • If the link was merely a "convenience link" to an online copy of material that originally appeared in print, and an appropriate substitute cannot be found, it is acceptable to drop the link but keep the citation.
  • If you cannot find the page on the Internet Archive, remember that you can often find recently deleted pages in Google's cache. They won't be there long, and it is no use linking to them, but this may let you find the content, which can be useful in finding an equivalent page elsewhere on the Internet and linking to that.

If none of those strategies succeed, do not remove the inactive reference, but rather record the date that the original link was found to be inactive — even inactive, it still records the sources that were used, and it is possible hard copies of such references may exist, or alternatively that the page will turn up in the near future in the Internet Archive, which deliberately lags by six months or more. When printed sources become outdated, scholars still routinely cite those works when referenced.

Tagging unsourced material

If an article has no or very few references, but you are unable to find them yourself, you can tag the article with the template {{Unreferenced}}.

If a particular claim in an article lacks citation and is doubtful, consider placing {{fact}} after the sentence or removing the claim. Consider the following in deciding which action to take:

  1. If it is doubtful but not harmful to the whole article, use the {{fact}} tag to ask for source verification, but remember to go back and remove the claim if no source is produced within a reasonable time.
  2. If it is doubtful and harmful, you should remove it from the article; you may want to move it to the talk page and ask for a source, unless you regard it is as very harmful or absurd, in which case it shouldn't be posted to a talk page either. Use your common sense. Don't be inappropriately cautious about removing unsourced material; it is better for Wikipedia to say nothing on an issue than to present false or misleading material.

All unsourced and poorly sourced contentious material about living persons should be removed from articles and talk pages immediately. It should not be tagged. See Wikipedia:Biographies of living persons and Wikipedia:Libel.

Tools

See also

References

Further reading

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