Citation

Anchor

• ref: ID for anchor. By default, anchors are always generated. The ordinary nonempty value |ref=ID generates an anchor with the given ID; such a linkable reference can be made the target of wikilinks to full references, especially useful in short citations like shortened notes and parenthetical referencing.

Identifiers

• id: A unique identifier, used where none of the specialized identifiers are applicable; wikilink or use an external link template as applicable. For example, |id=NCJ 122967 will append "NCJ 122967" at the end of the citation. You can use templates such as |id={{NCJ|122967}} to append NCJ 122967 instead.

The following identifiers create links and are designed to accept a single value. Using multiple values or other text will break the link and/or invalidate the identifier. In general, the parameters should include only the variable part of the identifier, e.g. |rfc=822 or |pmc=345678.

• arxiv: arXiv identifier; for example: |arxiv=hep-th/9205027 (before April 2007) or |arxiv=0706.0001 (April 2007 – December 2014) or |arxiv=1501.00001 (since January 2015). Do not include extraneous file extensions like ".pdf" or ".html". Aliases: eprint.
• asin: Amazon Standard Identification Number; if first character of asin value is a digit, use isbn. Because this link favours one specific distributor, include it only if standard identifiers are not available. Example |asin=B00005N5PF. Aliases: ASIN.
  • asin-tld: ASIN top-level domain for Amazon sites other than the US; valid values: ae, au, br, ca, cn, de, es, fr, in, it, jp, mx, nl, pl, sa, se, sg, tr, uk. Aliases: none.
• bibcode: bibcode; used by a number of astronomical data systems; for example: 1974AJ.....79..819H. Aliases: none.
• biorxiv: bioRxiv id, as in the entire DOI (e.g. 10.1101/078733 for http://biorxiv.org/content/early/2016/10/01/078733 or https://doi.org/10.1101/078733; 10.1101/2020.07.24.220400 for https://doi.org/10.1101/2020.07.24.220400). Aliases: none.
• citeseerx: CiteSeerX id, a string of digits and dots found in a CiteSeerX URL (e.g. 10.1.1.176.341 for http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.176.341). Aliases: none.
• doi: Digital object identifier; for example: 10.1038/news070508-7. It is checked to ensure it begins with (10.). Aliases: DOI.
  • Supports accept-this-as-written markup to indicate valid DOIs using a non-standard format, see below.
  • doi-broken-date: Date a valid DOI was found to be non-working/inactive at https://doi.org. Use the same format as other dates in the article. Aliases: none.
• eissn: International Standard Serial Number for the electronic media of a serial publication; eight characters may be split into two groups of four using a hyphen, but not an en dash or a space; example |eissn=1557-2986. Aliases: EISSN.
  • Supports accept-this-as-written markup to indicate valid eISSNs using a non-standard format, see below.
• hdl: Handle System identifier for digital objects and other resources on the Internet; example |hdl=20.1000/100. Aliases: HDL.
• isbn: International Standard Book Number; for example: 978-0-8126-9593-9. (See Wikipedia:ISBN and ISBN § Overview.) Hyphens in the ISBN are optional, but preferred. Use the ISBN actually printed on or in the book. Use the 13-digit ISBN – beginning with 978 or 979 – when it is available. If only a 10-digit ISBN is printed on or in the book, use it. ISBNs can be found on the page with the publisher's information – usually the back of the title page – or beneath the barcode as a number beginning with 978 or 979 (barcodes beginning with any other numbers are not ISBNs). For sources with the older 9-digit SBN system, use sbn. Do not convert a 10-digit ISBN to 13-digit by just adding the 978 prefix; the last digit is a calculated check digit and just making changes to the numbers will make the ISBN invalid. This parameter should hold only the ISBN without any additional characters. It is checked for length, invalid characters – anything other than numbers, spaces, and hyphens, with "X" permitted as the last character in a 10-digit ISBN – and the proper check digit. Aliases: ISBN.
  • Supports accept-this-as-written markup to indicate valid ISBNs using a non-standard format, see below.
• ismn: International Standard Music Number; for example: 979-0-9016791-7-7. Hyphens or spaces in the ISMN are optional. Use the ISMN actually printed on or in the work. This parameter should hold only the ISMN without any additional characters. It is checked for length, invalid characters – anything other than numbers, spaces, and hyphens – and the proper check digit. Aliases: ISMN.
• issn: International Standard Serial Number; eight characters may be split into two groups of four using a hyphen, but not an en dash or a space; example |issn=2049-3630. Aliases: ISSN.
  • Supports accept-this-as-written markup to indicate valid ISSNs using a non-standard format, see below.
• jfm: Jahrbuch über die Fortschritte der Mathematik; do not include "JFM" in the value; example |jfm=53.0144.01. Aliases: JFM.
• jstor: JSTOR reference number; for example: |jstor=3793107. Aliases: JSTOR.
• lccn: Library of Congress Control Number. When present, alphabetic prefix characters are to be lower case and without a space; example |lccn=79-57364 or |lccn=2004042477 or |lccn=e09001178. Aliases: LCCN.
• mr: Mathematical Reviews; example |mr=630583. Aliases: MR.
• oclc: OCLC Number for looking up publications in the WorldCat union catalog; example |oclc=9355469. Aliases: OCLC.
• ol: Open Library identifier; do not include "OL" in the value; example |ol=7030731M. Aliases: OL.
• osti: Office of Scientific and Technical Information; example |osti=4367507. Aliases: OSTI.
• pmc: PubMed Central; use article number for open repository full-text of a journal article, e.g. |pmc=345678. Do not include "PMC" in the value. See also the pmid parameter, below; these are two different identifiers. Aliases: PMC.
  • pmc-embargo-date: Date that pmc goes live; if this date is in the future, then pmc is not linked until that date. Aliases: none.
• pmid: PubMed; use unique identifier; example |pmid=17322060 See also the pmc parameter, above; these are two different identifiers. Aliases: PMID.
• rfc: Request for Comments; example |rfc=3143. Aliases: RFC.
• sbn: Standard Book Number; example |sbn=356-02201-3. Aliases: SBN.
  • Supports accept-this-as-written markup to indicate valid SBNs using a non-standard format, see below.
• ssrn: Social Science Research Network; example |ssrn=1900856. Aliases: SSRN.
• s2cid: Semantic Scholar corpus ID; example |s2cid=37220927. Aliases: S2CID.
• zbl: Zentralblatt MATH; example |zbl=0472.53010 For zbMATH search results like JFM 35.0387.02 use |jfm=35.0387.02. Aliases: ZBL.

In very rare cases, valid identifiers (f.e., as actually printed on publications) do not follow their defined standard format or use non-conforming checksums, which would typically cause an error message to be shown. Do not alter them to match a different checksum. In order to suppress the error message, some identifiers (|doi=, |eissn=, |isbn=, |issn=, and |sbn=) support a special accept-this-as-written markup which can be applied to disable the error-checking (as |<param>=((<value>))). If the problem is down to a mere typographical error in a third-party source, correct the identifier value instead of overriding the error message.

For some identifiers, it is possible to specify the access status using the corresponding |<param>-access= parameter.

For {{Cite journal}}, some identifiers (specifying free resources) will automatically be linked to the title when |url= and |title-link= are not used to specify a different link target. This behaviour can be overridden by one out of a number of special keywords for |title-link= to manually select a specific source (|title-link=pmc or |title-link=doi) for auto-linking or to disable the feature (|title-link=none).

It is not necessary to specify a URL to a link identical to a link also produced by an identifier. The |url= parameter (or |title-link=) can then be used for providing a direct deep link to the corresponding document or a convenience link to a resource that would not otherwise be obviously accessible.

Quote

• quote: Relevant text quoted from the source. Displays enclosed in quotes. If script-quote is defined, use quote to hold a Romanization (if available) of the text in script-quote.
  • script-quote: Original quotation for languages that do not use a Latin-based script (Arabic, Chinese, Cyrillic, Greek, Hebrew, Japanese, Korean, etc.); not italicized, follows italicized Romanization defined in quote (if available). Alias: none. Must be prefixed with one of the supported language codes to help browsers properly display the script:
    ... |quote=Tōkyō tawā |script-quote=ja:東京タワー |trans-quote=Tokyo Tower ...
  • trans-quote: English translation of the quotation if the source quoted is in a foreign language. Displays in square brackets. Alias: none.
• quote-page: The number of a single page quoted in |quote=. Use either |quote-page= or |quote-pages=, but not both. Should be a subset of the page(s) specified in |page=, |pages= or |at=. Displays preceded by p. unless |no-pp=yes. If hyphenated, use {{Hyphen}} to indicate this is intentional (e.g. |quote-page=3{{hyphen}}12). Alias: none.
• OR: quote-pages: A list or range of pages quoted in |quote=. Use either |quote-page= or |quote-pages=, but not both. Should be a subset of the pages specified in |pages= or |at=. Separate using an en dash (–); separate non-sequential pages with a comma (,). Displays preceded by pp. unless |no-pp=yes is defined. Hyphens are automatically converted to en dashes; if hyphens are appropriate because individual page numbers contain hyphens, for example: pp. 3-1–3-15, use double parentheses to tell the template to display the value of |quote-pages= without processing it, and use {{Hyphen}} to indicate to editors that a hyphen is really intended: |quote-pages=((3{{hyphen}}1{{ndash}}3{{hyphen}}15)). Alias: none.

Laysummary

These parameters are deprecated. If the source that they name is important to the Wikipedia article, create a separate cs1|2 template for that source.

• lay-url: (deprecated) URL link to a non-technical summary or review of the source; the URL title is set to "Lay summary".
  • lay-source: (deprecated) Name of the source of the lay summary. Displays in italics and preceded by a spaced endash.
  • lay-date: (deprecated) Date of the lay summary. Displays in parentheses.
  • lay-format: (deprecated) File format of the work referred to by lay-url; for example: PDF, DOC, or XLS; displayed in parentheses after lay summary. HTML is implied and should not be specified. File format annotation is automatically rendered when a PDF icon is displayed. Does not change the external link icon. Note: External link icons do not include alt text; thus, they do not add file format information for the visually impaired. See Using |format=

Display options

• mode: Sets element separator, default terminal punctuation, and certain capitalization according to the value provided. For |mode=cs1, element separator and terminal punctuation is a period (.); where appropriate, initial letters of certain words are capitalized ('Retrieved...'). For |mode=cs2, element separator is a comma (,); terminal punctuation is omitted; where appropriate, initial letters of certain words are not capitalized ('retrieved...'). To override default terminal punctuation use postscript.
• author-mask:
• contributor-mask:
• editor-mask:
• interviewer-mask:
• subject-mask:
• translator-mask:
  Replaces the name of the (first) author with em dashes or text. Set <name>-mask to a numeric value n to set the dash n em spaces wide; set <name>-mask to a text value to display the text without a trailing author separator; for example, "with". The numeric value 0 is a special case to be used in conjunction with <name>-link—in this case, the value of <name>-link will be used as (linked) text. In either case, you must still include the values for all names for metadata purposes. Primarily intended for use with bibliographies or bibliography styles where multiple works by a single author are listed sequentially such as shortened footnotes. Do not use in a list generated by {{reflist}}, ‎ or similar as there is no control of the order in which references are displayed. Mask parameters can take an enumerator in the name of the parameter (e.g. |authorn-mask=) to apply the mask to a specific name.

• display-authors:
• display-contributors:
• display-editors:
• display-interviewers:
• display-subjects:
• display-translators:
  Controls the number of author or editor names that are displayed when a citation is published. To change the displayed number of names, set display-authors and/or display-editors to the desired number. For example, |display-authors=2 will display only the first two authors in a citation (and not affect the display of editors). Likewise, |display-editors=2 will display only the first two editors (and all authors). |display-authors=0 and |display-editors=0 are special cases suppressing the display of all authors or editors including the et al. By default, all authors and editors are displayed. |display-authors=etal displays all authors in the list followed by et al. Aliases: none.
• postscript: Controls the closing punctuation for a citation; defaults to none. Additional text, or templates that render more than a single terminating punctuation character, will generate a maintenance message. |postscript= is ignored if quote is defined.

Subscription or registration required

Citations of online sources that require registration or a subscription are acceptable in Wikipedia as documented in Verifiability § Access to sources. As a courtesy to readers and other editors, editors should signal restrictions on access to material provided via the external links included in a citation. These levels describe requirements or constraints related to accessing and viewing the cited material; they are not intended to indicate the ability to reuse, or the copyright status, of the material, since that status is not relevant to verifying claims in articles.

Four access levels can be used:

• access indicator for named identifiers:
  • free: the source is free to read for anyone
• access indicators for url-holding parameters:
  • registration: a free registration with the provider is required to access the source, even if a limited preview, abstract or review may still be available without registration
  • limited: there are other constraints (such as a cap on daily views) to freely access this source
  • subscription: the source is only accessible via a paid subscription with the provider of the source ("paywall")

As there are often multiple external links with different access levels in the same citation, each value is attributed to a specific external link.

Access indicators for url-holding parameters

Online sources linked by |url=, |article-url=, |chapter-url=, |contribution-url=, |entry-url=, |map-url=, and |section-url= are presumed to be free-to-read. When they are not free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. Because the sources linked by these url-holding parameters are presumed to be free-to-read, they may not be marked as free.

URL-holding and access-indicator parameters

URL	Access	Allowed keywords
|url=	|url-access=	registration limited subscription
|article-url=	|article-url-access=
|chapter-url=	|chapter-url-access=
|contribution-url=	|contribution-url-access=
|entry-url=	|entry-url-access=
|map-url=	|map-url-access=
|section-url=	|section-url-access=

For example, this cites a web page that requires registration but not subscription:

{{cite web |url=https://example.com/nifty_data.php |url-access=registration |date=2021-04-15 |title=Nifty example data}}

which renders as:

"Nifty example data". 2021-04-15.

Access indicator for named identifiers

Links inserted by named identifiers are presumed to lie behind a paywall or registration barrier – exceptions listed below. When they are free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. When the sources linked by these named-identifier parameters are not presumed to carry a free-to-read full text (for instance because they're just abstracting services), they may not be marked as limited, registration, or subscription.

Named-identifier and access-indicator parameters

Identifier	Access	Allowed keywords
|bibcode=	|bibcode-access=	free
|doi=	|doi-access=
|hdl=	|hdl-access=
|jstor=	|jstor-access=
|ol=	|ol-access=
|osti=	|osti-access=
|s2cid=	|s2cid-access=

Some named-identifiers are always free-to-read. For those named identifiers there are no access-indicator parameters; the access level is automatically indicated by the template. These named identifiers are:

• |arxiv=
• |biorxiv=
• |citeseerx=
• |pmc=
• |rfc=
• |ssrn=

For embargoed pmc that will become available in the future, see pmc-embargo-date.

Examples

Books

{{Citation | last1  = Lincoln | first1 = A. | last2  = Washington | first2 = G. | last3  = Adams | first3 = J. | lastauthoramp = yes | title     = All the Presidents' Names | publisher = The Pentagon | place     = Home Base, New York | volume  = XII | edition = 2nd | year    = 2007 }} 

Web

{{Citation | url   = http://nrhp.focus.nps.gov/ | title = NPS Focus | work  = National Register of Historic Places | publisher  = [[National Park Service]] | accessdate = November 30, 2010 }} 

{{Citation | url = http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html | title = Earth's Atmosphere | accessdate = October 25, 2007 | publisher  = [[National Aeronautics and Space Administration]] | year   = 1995 | author = NASA | archiveurl = https://web.archive.org/web/20071013232332/http:// liftoff.msfc.nasa.gov/academy/space/atmosphere.html | archivedate = October 13, 2007 }} 

Journals, newspapers, magazines, or other periodicals

{{Citation | last  = Hill | first = Marvin S. | title = Joseph Smith and the 1826 Trial: New Evidence and New Difficulties | journal = BYU Studies | volume  = 12 | issue   = 2 | year    = 1976 | pages   = 1–8 | url     = https://byustudies.byu.edu/shop/PDFSRC/12.2Hill.pdf }} 

{{Citation | last1  = Mandelkern | first1 = M, | last2  = Elias | first2 = J, | last3  = Eden | first3 = D, | last4  = Crothers | first4 = D | display-authors = 2 | title   = The dimensions of DNA in solution | journal = J Mol Biol | volume  = 152 | issue   = 1 | pages   = 153–61 | year    = 1981 | pmid    = 7338906 | doi     = 10.1016/0022-2836(81)90099-1 }} 

{{Citation | last  = Smith | first = Joseph III | author-link = Joseph Smith III | title = Last Testimony of Sister Emma | newspaper = The Saints' Herald | publication-place = Plano, IL | volume = 26 | issue  = 19 | date   = October 1, 1879 | year   = 1879 | page   = 289 | url    = http://www.sidneyrigdon.com/dbroadhu/ IL/sain1872.htm#100179 }} 

{{Citation | last  = Sullivan | first = D.B. | contribution = Time and frequency measurement  at NIST: The first 100 years | year  = 2001 | title = 2001 IEEE Int'l Frequency Control Symp. | publisher = National Institute of Standards and Technology | url       = http://tf.nist.gov/timefreq/general/pdf/1485.pdf | format    = PDF }} 

Parts of books, including encyclopedia articles

{{Citation | last  = Bidamon | first = Emma Smith | author-link = Emma Hale Smith | chapter = Letter to Emma S. Pilgrim | date = March 27, 1876 | year = 1876 | editor-last  = Vogel | editor-first = Dan | title  = Early Mormon Documents | volume = 1 | publisher = Signature Books | publication-date = 1996 | isbn = 1-56085-072-8 }} 

{{Citation | editor-last  = Vogel | editor-first = Dan | title  = Early Mormon Documents | volume = 1 | publisher = Signature Books | publication-date = 1996 | isbn = 1-56085-072-8 }} 

{{Citation | last  = Kramer | first = Martin | author-link  = Martin Kramer | contribution = Bernard Lewis | editor-last  = Boyd | editor-first = Kelley | title = Encyclopedia of Historians and Historical Writing | volume = 1 | pages  = 719–720 | publisher = Fitzroy Dearborn | place = London | publication-date = 1999 | contribution-url = http://www.geocities.com/ martinkramerorg/BernardLewis.htm }} 

{{Citation | contribution = Bernard Lewis | editor-last = Boyd | editor-first = Kelley | title = Encyclopedia of Historians and Historical Writing | volume = 1 | pages = 719–720 | publisher = Fitzroy Dearborn | place = London | year = 1999 | contribution-url = http://www.geocities.com/ martinkramerorg/BernardLewis.htm }} 

Republications, or edited quotations in a periodical article

{{Citation | last = Knight | first = Joseph, Sr. | year = 1833 | editor-last = Jessee | editor-first = Dean | title = Joseph Knight's Recollection of Early Mormon History | journal = BYU Studies | volume = 17 | issue = 1 | publication-date = 1976 | page = 35 | url = https://byustudies.byu.edu/shop/PDFSRC/17.1Jessee.pdf }}

{{Citation | last = Klingensmith | first = Philip | contribution = Affidavit | year = 1872 | date = September 5, 1872 | place = Lincoln County, Nevada | title = Mountain Meadows Massacre | editor-last = Toohy | editor-first = Dennis J. | journal = Corinne Daily Reporter | publication-date = September 24, 1872 | publication-place = Corinne, Utah | volume = 5 | issue = 252 | page = 1 | contribution-url = http://udn.lib.utah.edu/u?/corinne,5359 }} 

Press release

{{Citation | url = http://www.apple.com/pr/library/2010/04/05ipad.html | title = Apple Sells Over 300,000 iPads First Day | publisher = Apple Inc | accessdate = April 10, 2010 | quote = in the US as of midnight Saturday, April 3}} 

Citing patents

Parameters (all are optional)

{{Citation | inventor-last = | inventor-first = | inventorlink = | inventor2-last = | inventor2-first = | inventorlink2 = | publication-date = | issue-date = | title = | country-code = | description = | patent-number = | ref = }}

Examples

{{Citation | inventor1-last = Degermark | inventor1-first = Mikael | inventor2-last = Brodnik | inventor2-first = Andrej | inventor3-last = Carlsson | inventor3-first = Svante | inventor4-last = Pink | inventor4-first = Stephen | title = Fast routing lookup system using complete prefix tree, bit vector, and pointers in a routing table for determining where to route IP datagrams | issue-date = 2001 | patent-number = 6266706 | country-code = US}} 

Anchored citations

This template can generate a citation that can be combined with shortened footnotes or parenthetical referencing. It does this by creating an HTML anchor containing an ID. The special parameter |ref=harv generates an ID suitable for Harvard referencing templates such as {{Harv}} as specified in the next section; this is the default for the {{Citation}} template. To disable anchor generation, specify |ref=none – leaving |ref= empty has the same effect but is ambiguous; this is the default for the Cite templates such as {{Cite book}} and {{Cite news}}. You can also specify the ID directly, using the |ref=ID parameter. For example, suppose an article's References section contains the markup:

• {{Citation |author=Sigmund Freud |title=Civilization and Its Discontents |year=1930 |ref=CivDis}}

which generates the citation:

• Sigmund Freud (1930), Civilization and Its Discontents

Then, the markup "([[#CivDis|Freud 1930]])" generates a parenthetical reference "(Freud 1930)" containing a wikilink to the citation (try clicking on the wikilink).

Anchors for Harvard referencing templates

IDs compatible with Harvard referencing templates such as {{Harv}} are computed from the last names of the authors and the year of the cited source. For example, the markup "{{harv|Wright|Evans|1851|p=ix}}" generates the Harvard reference "(Wright & Evans 1851, p. ix)", which wikilinks to the citation whose markup and appearance are shown below:

• {{Citation |last1=Wright |first1=Thomas |last2=Evans |first2=R. H. |title=Historical and Descriptive Account of the Caricatures of James Gillray |location=London |publisher=Henry G. Bohn |year=1851 |oclc=59510372}}
• Wright, Thomas; Evans, R. H. (1851), Historical and Descriptive Account of the Caricatures of James Gillray, London: Henry G. Bohn, OCLC 59510372

In this example the {{Citation}} template defines, and the {{Harv}} template uses, the HTML ID "CITEREFWrightEvans1851", composed by concatenating the string "CITEREF" with the last names of the authors and the year. The {{Harvid}} template can be used to generate such IDs, for example, {{harvid|Wright|Evans|1851}} generates "CITEREFWrightEvans1851".

Related methods which leave only a number in the text are to use the {{Harvnb}} template enclosed in the html code, or to use the {{Sfn}} template alone. The example above would be {{harvnb|Wright|Evans|1851|p=ix}} or {{sfn|Wright|Evans|1851|p=ix}} both of which generate a footnote, such as

17. Wright & Evans 1851, p. ix

The names of only the first four authors are used; other author names are not concatenated to the ID. If no author names are given, editor names are used instead. For patents, inventor names are used instead of authors or editors. If these names are not given, this template does not generate an anchor.

Last names are used, as specified by the parameters |last1= (or |last=), |last2=, |last3=, and |last4=, and similarly for |editor1-last= etc. and for |inventor1-last= etc. If a full name is given but no last name is specified, this template falls back on the full name, but this usage is not recommended. For example, in "{{Citation | author = Sigmund Freud | title = The Ego and the Id | year = 1923}}" no last name is given, so this citation cannot be combined with the Harvard reference "{{harv|Freud|1923}}". To make these {{Citation}} and {{Harv}} invocations compatible, either replace "|author=Sigmund Freud" with "|first=Sigmund |last=Freud", or add "|ref={{harvid|Freud|1923}}" to the {{Citation}} invocation, or add the same ref parameter (say, "|ref=EgoId") to both the {{Citation}} and the {{Harv}} invocations.

Similarly, the year is used, as specified by |year=. If no year is given, this template attempts to derive the year from |date= (or, if no date is given, from |publication-date=) by applying the MediaWiki#time function. This heuristic works with many common date formats (American, International and ISO 8601 standard format YYYY-MM-DD as listed in WP:MOS), but may not work as expected with other formats, so when in doubt it may be safer to use |year=. Note that if only a year, say 2005, is known you must use |year=2005 rather than |date=2005.

IDs must be unique

Names, years, and hand-specified IDs must be chosen so that the IDs are unique within a page; otherwise the HTML will not conform to the W3C standards, and any references to the citations will not work reliably. For example, suppose a page contains the following two citations with {{Harv}}-compatible IDs:

• Montes, G.; Halterman, J. S. (2008a), "Association of Childhood Autism Spectrum Disorders and Loss of Family Income", Pediatrics, 121 (4): e821–6, doi:10.1542/peds.2007-1594, PMID 18381511
• Montes, G.; Halterman, J. S. (2008b), "Child Care Problems and Employment Among Families with Preschool-aged Children with Autism in the United States", Pediatrics, 122 (1): e202–8, doi:10.1542/peds.2007-3037, PMID 18595965

If these citations were altered to say "2008" rather than "2008a" and "2008b", the resulting page would not work, because the two different citations would both attempt to use the ID "CITEREFMontesHalterman2008". To avoid this problem, distinguish the citations by appending suffixes to the years, e.g., "|year=2008a" and "|year=2008b", as was done above. Any Harvard references to these citations should use years with the same suffixes.

It is good practice to verify that a page does not contain duplicate IDs by using the W3C Markup Validation Service; see External links.

Dates