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This guideline is a part of the English Wikipedia's Manual of Style.

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.

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[[:|WP:CITE
WP:REF]]

This page is a style guide, describing how to write citations in articles. Providing sources for edits is mandated by Wikipedia:No original research and Wikipedia:Verifiability, which are policy. This means that any material that is challenged and has no source may be removed by any editor. See those pages and Wikipedia:Reliable sources for more information. For information about the importance of using good sources in biographies of living persons, see Wikipedia:Biographies of living persons, which is policy.

Attribution is especially needed for direct quotes, information that is contentious or likely to be challenged, and superlatives and absolutes (such as statements that something is the best, first or only one of its kind). If you don't know how to format the citation, others will fix it for you. Simply provide any information you can.

Why sources should be cited

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 credit a source for providing useful information and to avoid claims of plagiarism.
To ensure that material about living persons is reliably sourced and complies with Wikipedia:Biographies of living persons.

Note: Wikipedia articles should not be cited as sources.

When to cite sources

When you add content

For ways to find sources to cite, see Finding good sources...

If you add any information to an article, particularly if it's contentious or likely to be challenged, you should supply a source. If you don't know how to format the citation, others can fix it for you. Simply provide any information you can.

In general, even if you are writing from memory, you should actively search for authoritative references to cite. If you are writing from your own knowledge, then you should know enough to identify good references that the reader can consult on the subject — you will not be around forever to answer questions. The main point is to help the reader and other editors.

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, mention them by name, 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 if you use a source to verify that material. Adding citations to an article 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 do this. Direct quotes, used as a method of easing factual verification, can be provided (in whatever format is agreed on by the main editors of the article) for any statement.

Text that is, or is likely to be, disputed

Think ahead. Try to imagine whether 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. When in doubt about whether something might be disputed, provide a specific citation.

Intermediate sources: State where you got it

A common error is to copy citation information from an intermediate source without acknowledging the original 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 and the web page must be mentioned. The web page itself must therefore be sufficiently reliable i.e. there must be good reason to assume that it cites the reliable source correctly. Your citation might only mention the web page, or you can provide further information like this:

<Web page>, which cites <book>, or
<Book>, cited at <web page>.

However, you shouldn't cite only the book unless you looked at it yourself. If you checked the book, it is no longer necessary to mention the web page but you can still mention it if that would be useful information for readers. You can do so using a form like this:

<Book> (also see <web page>).

When adding material to the biography of a living person

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 larger quotes, you may wish to use Template:Quotation.

What sources to cite

Prefer credible third-party, peer-reviewed English-language sources.

How and where to cite sources

See also: Wikipedia:Citations quick reference.

When writing a new article or adding references to an existing article that has none, follow the established practice for the appropriate profession or discipline that the article is concerning (if available and unquestioned).
An article's previous content contributors usually know the established practice - if possible, follow their lead if the article already has references.
If the established practice is unavailable or disputed, contributors should decide on a style that they believe strikes an appropriate balance between preserving the readability of the text and making citations as precise and accessible as possible.
If contributors differ as to the appropriate style of citation, they should defer to the article's main content contributors in deciding the most suitable format for the presentation of references. If no agreement can be reached, the citation style used should be that of the first major contributor.
When sources are mentioned within the body of an article, it is helpful to identify them clearly on the first mention. 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 ..."
It is helpful to briefly mention in the footnote what claim it is that is being referenced. This allows later editors to tell whether it's a phrase, sentence or paragraph that's being documented, and also to find undocumented claims sneaking into paragraphs that were otherwise referenced.

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 in the talk page, or in a comment on the main page, and ask others how to format it correctly for that article.

See below for a discussion of different citation styles.

For an easy-to-follow guide, see Wikipedia:Citing sources/example style
Some editors prefer to use templates to format references; see the summary of citation templates; for users familiar with the citation process, seeking a reference, a quick reference exists.
Landmark Citation Machine is also good for making bibliographies. It is regularly updated and runs on three separate servers.
Wikicite is a free program that helps people to properly reference their Wikipedia contributions. It is written in Visual Basic .NET, making it suitable only for Windows 2000 and Windows XP users. Wikicite and its source code is freely available, see the developer's user page for further details.

The system of presenting references in a Wikipedia article may change over time; it is more important to have clarity and consistency in an article than to adhere to any particular system.

Remember: the most important thing is to enter comprehensive reference information — that is, enough information so that a reader can find the original source with relative ease.

Templates

The use of Citation templates is not required by WP:CITE, and is neither encouraged nor discouraged by any other Wikipedia citation 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, while other editors find them annoying, particularly when used inline in the text. Because they are optional, editors should not change articles from one style to the other without consensus.

Page numbers

When citing books and articles, provide page numbers where appropriate. 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.

According to Jessica Benjamin, one weakness of radical politics has been "to idealize the oppressed, as if their politics and culture were untouched by the system of domination, as if people did not participate in their own submission" (Benjamin 1988:9).
Jessica Benjamin has argued that radical politics has been weakened by its inattention to the ways oppressed people participate in their own oppression (Benjamin 1988:9).

Page numbers are not required when a citation accompanies a general description of a book or article, or when a book or article, as a whole, is being used to exemplify a particular point of view.

In the 1980s several feminists explored feminist readings of psychoanalytical thought (e.g. Gallop 1985, Hamilton 1982, Rose 1986, Benjamin 1988).
Jessica Benjamin, for example, has drawn on Freudian and feminist theory to argue that in modern Western society, the relationship between males and females is paradigmatic for a variety of relations of domination and submission" (Benjamin 1988).

Citation styles

The following are different citation styles you can use to insert references into Wikipedia articles:

All three are acceptable citation styles for Wikipedia. Do not change from Harvard referencing to footnotes or vice versa without checking for objections on the talk page. If there is no agreement, prefer the style used by the first major contributor.

Embedded HTML links

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]

Then in the References section, a full citation is provided:

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

which appears as:

"Sorrell accuses Murdoch of panic buying" by John Plunkett, The Guardian, October 27, 2005, retrieved October 27, 2005

Harvard referencing

The Harvard referencing system places a partial citation — the author's name and year of publication within parentheses — at the end of the sentence within the text, and a complete citation 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).

For one author, add the author's surname and the year of publication in parentheses (round brackets) after the sentence or paragraph, and before the period: for example (Smith 2005).
For two authors, use (Smith & Jones 2005); for more authors, use (Smith et al. 2005).
If the "References" section contains two or more works by the same author but published the same year, use a letter after the year to distinguish the different sources (for example, (Smith 2005a) and (Smith 2005b). Make sure that the in-text citations use the correct letters that correspond to the full citation in the "References" at the end of the article.

If the date of publication is unavailable, use "n.d." (meaning, no date)

Many times authors use an edition of a book that was published long after the original publication. In such cases, many people put the original date of publication in square brackets followed by the date of publication of the edition used by the author who is making the citation. For example, a citation might be

(Marx [1867] 1967)

And the complete reference would be:

Marx, Karl. [1867] (1967). Capital: A Critique of Political Economy Vol. I. Edited by Frederick Engels. New York: International Publishers. ISBN 1-899235-74-4

When providing a page number, the convention is (Smith 2005:73).
For a quotation that is within the text and marked by quotation marks, the citation follows the end-quotation mark ("), and is placed before the period (.), "like this" (Smith 2005).
For a quotation that is indented, the citation is placed after the period, like the following. (Smith 2005)
When the author of the reference is named as part of the text itself, put the year in parentheses; for example "Smith (2005) says..."

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

Complete citations in a "References" section

Complete citations, also called "references", are collected at the end of the article under a ==References== heading. Under this heading, list the comprehensive reference information as a bulleted (*) list, one bullet per reference work. Try to make sure that whichever citation system you choose is used consistently throughout the article. Note that citation templates are not required, though they may be used at the discretion of individual editors.

References typically include: the name of the author, the title of the book or article, and the date of publication. Different professions, academic disciplines, and publishers have different conventions as to the order in which this information should be arranged, or whether additional information is required. Usually, the list is in alphabetical order by the author's surname. The name of the publisher and its city is optional. The ISBN of a book is optional. Journal articles should include volume number, issue number and page numbers, if available.

Typical references would be:

McDougall, D. (2003). "Trauma of quake's shattered children". Guardian. Retrieved October 23, 2005.
Smith, J. How to cite your sources, Random House, 2005. ISBN 1-899235-74-4

or using a template:

* {{cite journal | author=L. Hussein ''et al.'' | title=Nutritional quality and the presence of anti-nutritional factors in leaf protein concentrates (LPC) | journal=International Journal of Food Sciences and Nutrition | year=1999 | volume=50 | issue=5 | pages= 333–343}}

which results in:

L. Hussein; et al. (1999). "Nutritional quality and the presence of anti-nutritional factors in leaf protein concentrates (LPC)". International Journal of Food Sciences and Nutrition. 50 (5): 333–343. {{cite journal}}: Explicit use of et al. in: |author= (help)

For more templates to assist formatting, see the citation templates.

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's online.

Some books have been reprinted several times over the course of the years. Sometimes they have gone through several editions, and sometimes a book may be published by several different publishers. This can raise serious problems for citations, because different editions may be paginated differently. Ideally, all citations in a given article should refer to the same edition by the same publisher, and this edition information should be included in the reference at the end of the article and/or the ISBN (see there) should be given. That way, there would be no confusion over the correct page number for cited quotes or material.

If the "References" section contains two or more works by the same author but published the same year, use a letter after the year to distinguish the different sources (for example 2005a and 2005b).
If you do not know the date of publication, try to find it (you could try your local library, the web-page of a national library such as the Library of Congress, or Amazon.com)
If the date of publication is unavailable, use "n.d." (meaning, no date)
Many times editors use an edition of a book that was published long after the original publication. In such cases, they must provide the date of the edition they are using or else the ISBN, and preferably both. This is important because different editions may be paginated differently.

As Wikipedia grows it is likely that different editors may rely on different editions of the same book.

Usually, different editions of the same book are published in different years. In such cases knowing the year is enough information to distinguish the different editions.
Sometimes, different editions of the same book are published in the same year. This often happens after a copyright has expired, and different publishing companies publish different editions. In such cases, one must know the publisher to distinguish the different editions, or else the ISBN.

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.

Footnotes

Technical issues with footnotes

Footnotes are treated as one of the two standard styles of citation in The Chicago Manual of Style.
Footnotes are normally simply numbered numerically. Thus, determining who said what typically requires a reader to continually jump back and forth between the main body and the footnote/endnote to see if there is something of value. When footnotes are simply providing a much more detailed argument, this is often not a problem, but if the footnotes are the primary citation method, this can be critical (since it is sometimes important to keep track of who claims what).
Until recently, the MediaWiki software had limited footnote support. In particular, automatic numbering of footnotes conflicted with use of embedded HTML links in single square brackets with automatic numbering, and the same footnote could not be used multiple times with automatic numbering, although this issue has now been addressed by the new <ref> element. (More details at Wikipedia:Footnotes)
Many of today's style guides require not using or recommend against using footnotes and reference endnotes to cite sources Template:Ref harvard. The APA style does not use footnotes to cite sources. The MLA style manual advocates use of parenthetical reference citations in texts, reducing reference footnotes and reference endnotes in favor of such embedded in-text parenthetical bibliographic references wherever possible; such embedded in-text parenthetical citations refer to attached lists of "Works Cited." Content footnotes and endnotes are still used in MLA format, however.
Editors should not switch from one citation system to another without checking on the talk page that there are no objections. For example, editors should not switch from footnotes to Harvard referencing, or vice versa. If no agreement can be reached, the system used by the first major contributor to use one should be deferred to. However, this advice does not apply to switching from one footnote style to another, which may simply constitute a technical improvement.

Note: If a Wikipedia article does use footnotes, the footnotes in their own section must include the normal source citations just as in the "References" section for other inline citations above.

Example

Many publications use numbers — in square brackets and/or superscripted — to refer to a list of citations at the end of the article, e.g. ^{[ 1 ]} or [1] with:

^ L. Hussein et al. (1999). "Nutritional quality and the presence of anti-nutritional factors in leaf protein concentrates (LPC)". International Journal of Food Sciences and Nutrition 50 (5): 333–343.

What footnotes are normally used for

Some publications use footnotes for both the full citation of a source, and for tangential comments or information of interest to the reader.
Some publications use Harvard style notation for sources, and use footnotes exclusively for tangential comments or information of interest. 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" section

Technically, footnotes appear at the bottom of a page; endnotes appear at the end of a chapter or book. Since Wikipedia articles may be considered to consist of one long page, or of no pages at all, Wikipedia footnotes appear at the end of an article, but are nevertheless called footnotes.

Recommended section names to use for footnotes in Wikipedia:

==Notes or Footnotes==
==Notes and references== section: Used if there is no separate section with general references, and if all sources of the general content of the article are covered by the footnotes, but see the note about this below.

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

It is helpful when footnotes are used that a 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 contains only citations, helps readers to see at a glance the quality of the references used.

What to do when a reference link "goes dead"

When a link in the Reference section (a link to a source for information in the article) "goes dead", it should be repaired or replaced if possible. External links/Further reading sections are not as important, but 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.

A very large proportion of pages can be recovered from the Internet Archive. Just go to http://www.archive.org/ 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.
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.

How to ask for citations

If an article needs references but you are unable to find them yourself, you can tag the article with the templates {{Unreferenced}}, {{Not verified}}, or {{Primarysources}}. It is often more useful to indicate specific statements that need references, by tagging those statements with {{fact}}. The {{citation needed}} and {{cn}} both redirect to the {{fact}} tag and may be preferred by some editors, for the sake of clarity or brevity. Do not use this tag in order to label text which appears doubtful or false. The {{verify source}} tag should be used to label text which appears doubtful or false, in order to request for source verification. All of these tags can be placed in the same place that you would place an inline reference.

To summarize the use of in line tags for unsourced or poorly sourced information:

if it is not doubtful, you may use {{fact}} or {{citequote}} tag to ask for better citation in order to make the article complete.
if it is doubtful but not too harmful to the whole article, you may use {{verify source}} tag to ask for source verification.
If it is doubtful and (quite) highly harmful, you may move it to the talk page and ask for a source.
If it is very doubtful and very harmful, you may remove it directly without the need of moving it to the talk page first.

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

Citing Wikipedia in other works

For suggestions on how to cite Wikipedia in other works, see Wikipedia:Citing Wikipedia; the tool Special:Cite is also available there to help you.

References

Concordia Libraries (Concordia University). Citation and Style Guides. Retrieved December 28, 2004. (This provides a list of common citation styles.)
Citation Styles Handbook: APA
Citation Styles Handbook: MLA
APA Style.org
Using American Psychological Association (APA) Format (Updated to 5th Edition)
Citing Electronic Documentation (APA, Chicago, MLA)
The Columbia Guide to Online Style
Ritter, R. (2002). The Oxford Style Manual. Oxford University Press. ISBN 0198605641
University of Chicago Press Staff. (2003). The Chicago Manual of Style, 15th edition. University Of Chicago Press. ISBN 0226104036

@@ Line 40: / Line 40: @@
 === Intermediate sources: State where ''you'' got it ===
-A common error is to copy citation information from an intermediate source without acknowledging the original 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 and the web page ''must'' be mentioned.  The web page itself must therefore be a [[WP:RS|reliable source]]. Your citation might ''only'' mention the web page, or you can provide further information like this:
+A common error is to copy citation information from an intermediate source without acknowledging the original 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 and the web page ''must'' be mentioned.  The web page itself must therefore be sufficiently reliable i.e. there must be good reason to assume that it cites the reliable source correctly. Your citation might ''only'' mention the web page, or you can provide further information like this:
 * <Web page>, which cites <book>, or