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Electronic References 

Electronic References

Cheryl Iverson

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PRINTED FROM AMA MANUAL OF STYLE ONLINE ( © American Medical Association, 2009. All Rights Reserved. Under the terms of the license agreement, an individual user may print out a PDF of a single chapter of a title in AMA Manual of Style Online for personal use (for details see Privacy Policy and Legal Notice).

Subscriber: null; date: 13 December 2018

Electronic References

  • The Internet made a lot of things very simple.
  • Bibliographies aren't among them.
  •     J. Kronholz10
  • … the basic rules of citation are still applicable
  • when referencing the Internet.
  •     K. Patrias11

Electronic references have become considerably more common since the publication of the ninth edition of this manual. Internet references, rather than being something that only authors, editors, publishers, and librarians fretted about, were the subject of a front-page article in the Wall Street Journal.10 Guidelines for handling electronic references are now readily available. Although the American Psychological Association12,13 was among the first to propose such guidelines, those of the National Library of Medicine (NLM)14 are more widely used for medical research.

Print and electronic references differ in several ways. Below are some issues to consider.

  • websites may be evanescent, vanishing much faster than books go out of print. To address this phenomenon, the NLM “strongly recommend[s] that the user produce a print or other copy when possible for future reference.”6(piii) Some journals recommend this to authors in their instructions.15 Dellavalle et al16 suggest that “the best current solution to improve access to Internet references is to require capture and submission of all Internet information at the time of manuscript consideration.” In preparing a reference list, authors should check to make sure any URLs (uniform resource locators) they cite are still valid; editors should check these again. Since typographical errors render URLs invalid, validation may be required several times in the publication process. Although it is desirable to have functional links, it is to be expected that, over time, some links may break as sites cease to exist, much as books may go out of print. Any updating of URLs in an effort to “fix” a link should be done with care, ensuring that the material that was cited originally still exists on the revised link.

  • Some publishers are using other less-transient identifiers instead of, or in addition to, URLs. Among these are the digital object identifier (DOI) and the PubMed identification number (PMID). The DOI may be used to identify not just individual journal articles, but any piece of content (eg, a single figure) within an article; DOIs may also be assigned to books and many other forms of intellectual content.

The DOI has 2 elements, separated by a forward slash: the prefix and the suffix. The prefix is assigned by a DOI registration agency (an organization may have multiple prefixes) and the suffix, which follows the prefix and a forward slash, identifies the particular item. All DOIs begin with 10. For example, in the DOI in example 6 below (10.1038/nature02312), “10.1038” is the prefix and “nature02312” is the suffix. (Note: Some publishers use other identifiers as a part of the suffix.) The DOIs can be any length and, once assigned, are not changed. To find an article using the DOI, a reader can enter the DOI in the search box on the DOI website ( or in some journal search engines.17 As close as possible to publication, it is advisable to check all DOIs to make sure that they resolve.

The PMID is assigned to the journal articles cited in a journal indexed by PubMed and is a part of the PubMed citation. To find an article, a reader can enter the PMID in the “search” box on the PubMed website ( Some journals publish the DOI with the article (see example 6 in 3.15.1, Online Journals); the PMID is usually not published but exists as a behind-the-scenes identifier.

  • websites may be updated much more frequently than published books or journals; thus, it is critical to provide the date that the author accessed the site and, if possible, the date on which the information was updated.

  • Some journals and books may be available in print and online, but these versions may not be identical: the differences may be as minor as the online correction of a typographical error discovered in the print journal, which is not formally corrected and is impossible to track (see 6.2.7, Editorial Assessment and Processing, Editorial Processing, Corrections), or as major as 2 versions of the same article, or situations in which additional material (eg, tables or figures) is available only online. Books are often adapted for the Web to enhance interactivity for readers and add features. Because of these possible differences between various versions, it is critical that authors cite the version consulted. Note: The cited version may not be the version of record (ie, the version that the publisher considers authoritative).

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