These 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.

When an URL is equivalent to the link produced by the corresponding identifier (such as a DOI), don't add it to any URL parameter but use the appropriate identifier parameter, which is more stable and may allow to specify the access status. The |url= parameter or title link can then be used for its prime purpose of providing a convenience link to an open access copy which would not otherwise be obviously accessible.

  • 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".
  • 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
    • asin-tld: ASIN top-level domain for Amazon sites other than the US; valid values: au, br, ca, cn, co.jp, co.uk, de, es, fr, it, mx
  • bibcode: Bibcode; used by a number of astronomical data systems; for example: 1974AJ.....79..819H. Comment: Techies are aware of the 2019 switch from old to new ADS URLs: the old URLs should continue working after October 2019 even though deprecated; see the April/May 2019 and June 2019 discussions.
  • biorxiv: bioRxiv id, a 6-digit number at the end of the biorXiv URL (e.g. 078733 for http://biorxiv.org/content/early/2016/10/01/078733 or https://dx.doi.org/10.1101/078733)
  • 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 )
  • doi: Digital object identifier; for example: 10.1038/news070508-7. It is checked to ensure it begins with (10.).
    • doi-broken-date: Date the DOI was found to be non-working at https://dx.doi.org. Use the same format as other dates in the article. Alias: doi-inactive-date
  • 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 Alias: EISSN
  • hdl: Handle System identifier for digital objects and other resources on the Internet; example hdl=20.1000/100 Alias: HDL
  • isbn: International Standard Book Number; for example: 978-0-8126-9593-9.
  • 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. Alias: 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 Alias: ISSN
  • jfm: Jahrbuch über die Fortschritte der Mathematik; example jfm=53.0144.01
  • jstor: JSTOR reference number; for example: jstor=3793107 will generate JSTOR 3793107.
  • lccn: Library of Congress Control Number. When present, alphabetic prefix characters are to be lower case; example lccn=2004042477
  • mr: Mathematical Reviews; example mr=630583
  • oclc: OCLC; WorldCat's Online Computer Library Center; example oclc=9355469
  • ol: Open Library identifier; do not include "OL" in the value; example ol=7030731M
  • osti: Office of Scientific and Technical Information; example osti=4367507
  • 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.
  • pmid: PubMed; use unique identifier; example pmid=17322060
  • rfc: Request for Comments; example rfc=3143
  • ssrn: Social Science Research Network; example ssrn=1900856
  • zbl: Zentralblatt MATH; example zbl=0472.53010 For zbMATH search results like JFM 35.0387.02 use jfm=35.0387.02