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.   arxiv: arXiv identifier; for example: arxiv=hep-th/9205027 (before April 2007) or arxiv=0706.0001 or arxiv=1501.00001 (since April 2007). 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.  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  doi: Digital object identifier; for example: 10.1038/news070508-7. It is checked to ensure it begins with ().  doi-broken-date: Date the DOI was found to be non-working at http://dx.doi.org. Use the same format as other dates in the article. Alias: doi_brokendate, doi-inactive-date  isbn: International Standard Book Number; for example: 978-0-8126-9593-9.  Dashes 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, prefix the number with a zero; thus, SBN 902888-45-5 should be entered as . 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. Alias: ISBN  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.  jfm: Jahrbuch über die Fortschritte der Mathematik  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.  mr: Mathematical Reviews  oclc: OCLC; WorldCat's Online Computer Library Center  ol: Open Library identifier; do not include "OL" in the value.  osti: Office of Scientific and Technical Information  pmc: PubMed Central; use article number for full-text free repository of a journal article, e.g. pmc=345678. Do not include "PMC" in the value.   embargo: Date that pmc goes live; if this date is in the future, then pmc is not linked until that date.  pmid: PubMed; use unique identifier.   rfc: Request for Comments  ssrn: Social Science Research Network  zbl: Zentralblatt MATH