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2006 MAY–JUNE; 350
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May 09, 2006 [posted]

Order of Authors in MEDLINE®/PubMed® Citations

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ighlights



The National Library of Medicine® (NLM) treatment of corporate authors has varied over the years as follows:

Corporate Authors
Year Citation Created PubMed Display How to Search PubMed
1966-1999 Corporate author(s) placed at end of article title. (See Figure 1.) lansoprazole helicobacter study group [ti]
2000-2006 April Corporate author(s) entered in separate field and always displayed last in the list of authors. (See Figure 2.) nisc comparative sequencing program [cn]
2006 May forward Corporate author(s) entered in separate field and displayed in the order found in the byline of the published article. (See Figure 3.) nisc comparative sequencing program [cn]

Background

In the past, the NLM recorded personal author names in bibliographic citations in the order in which the names appear in the byline of the published article. However, corporate authors (also known as group authors or collective authors/names) were placed at the end of the article title field in the citation as there was no separate field for corporate authors in the MEDLINE database (see Figure 1).

Misiewicz JJ, Harris AW, Bardhan KD, Levi S, O'Morain C, Cooper BT, Kerr GD, Dixon MF, Langworthy H, Piper D.
One week triple therapy for Helicobacter pylori: a multicentre comparative
study. Lansoprazole Helicobacter Study Group.
Gut. 1997 Dec;41(6):735-9.
PMID: 9462204 [PubMed - indexed for MEDLINE]

Figure 1: PubMed Summary display of Personal and
Corporate Authors in citations created prior to 2000.

When NLM reinvented its systems and moved its databases from the mainframe computer environment to newer relational database technology on servers, it redefined and reorganized some data. One improvement around the year 2000 was the introduction of the <CollectiveName> XML (eXtended Markup Language) element specifically for corporate or group authors as part of the <AuthorList> set of elements in MEDLINE/PubMed. NLM had observed that group authorship was becoming more prevalent as a result of group and multicenter studies.

The new data element was effective for newly created MEDLINE/PubMed citations only. NLM made the decision to place these collective names for prospective citations at the end of the list of personal authors using semicolon punctuation to separate them from personal authors (see Figure 2). Existing citations with corporate authors in the article title element were not changed. NLM attempted to isolate the corporate authors at the end of the article titles in retrospective citations to move them to the new data element, but the risk of corrupting the data was too great. Many titles consist of delineated pieces such as a main title followed by a subtitle and it was not possible to distinguish accurately between subtitles and corporate authors given the resources available at that time.

Margulies EH, Maduro VV, Thomas PJ, Tomkins JP, Amemiya CT, Luo M, Green ED; NISC Comparative Sequencing Program.
Comparative sequencing provides insights about the structure and conservation of marsupial and monotreme genomes.
Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3354-9. Epub 2005 Feb 17.
PMID: 15718282 [PubMed - indexed for MEDLINE]

Figure 2: PubMed Summary display of Personal and
Corporate Authors in citations created from about 2000 until May 2006.

New PubMed Displays of Author Names

The Summary, Abstract, and Citation Displays in PubMed now show the authors, regardless of whether they are personal or corporate authors, in the order in which they appear in the byline in the published article. A mixture of punctuation to separate the authors is used with personal authors still separated by a "comma space" and corporate authors preceded by a "semicolon space." The complete author list still ends with a period (see a mocked-up version of an old citation in Figure 3).

Margulies EH; NISC Comparative Sequencing Program; Maduro VV, Thomas PJ, Tomkins JP, Amemiya CT, Luo M, Green ED.
Comparative sequencing provides insights about the structure and conservation of marsupial and monotreme genomes.
Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3354-9. Epub 2005 Feb 17.
PMID: 15718282 [PubMed - indexed for MEDLINE]

Figure 3: PubMed Summary display of Personal and
Corporate Authors in citations created from May 2006
forward (using an old citation for easy comparison with Figure 2).


For Figure 3, the published article lists the group author NISC Comparative Sequencing Program as the second author in the byline, preceded and followed by personal authors.

Note that the corporate author is both preceded by and followed by a "semicolon space" when it occurs inside the list rather than as the first or last author. If the corporate author is the first author, it is followed by a "semicolon space" when additional authors are present. If the corporate author is the only author, it is followed by a period. If the corporate author is the last author, it is preceded by a "semicolon space" and is followed by a period. Sometimes the corporate author is the only entry in the byline but the article, through the use of an asterisk or some other mechanism, will indicate personal authors responsible for the writing of the article. In this case, NLM puts the corporate author first and then lists the personal authors found elsewhere in the article.

The MEDLINE display still shows the authors in a vertical list, each preceded by a mnemonic (AU for personal author, FAU for full name of personal author, and CN for corporate author). Now, however, the CN field may appear interspersed with the AU/FAU fields rather than only at the end of the AU/FAU occurrences.

A mixture of punctuation in the author list follows the guidance of NISO Z39.29-2005 Bibliographic References, is thought to be less disruptive to current users of the MEDLINE/PubMed citation data (including those who base their own citation formats on the NLM style), and provides a way, both visually and mechanically, for the corporate author(s) to be identified in a paragraph-style citation.

Sorting by Authors in PubMed

Sorting by first or last author in PubMed is based only on personal author names, unless a citation does not have any personal authors but does have one or more corporate authors, in which case the corporate author is used for the sort.

Effective Date for New Order of Authors

NLM implemented the new order of authors in May 2006. The change is effective for newly created citations only. If NLM is alerted to citations where the order of the author names is not as shown in the published article, NLM will review those citations on a case-by-case basis as time permits for possible changes.

Reasons for the Change

NLM decided to make the change in presentation order for authors for the following reasons:

  1. NISO Z39.29-2005 Bibliographic References, the US National Standard for how to cite bibliographic materials, states that authors should be listed in the citation in the order in which the names appear in the byline of the published article.

  2. Users of MEDLINE/PubMed have requested that NLM citations reflect the published order of authors, regardless of personal versus group status in the byline.

  3. Statistical analysis of the MEDLINE data shows an increasing trend in the occurrence of corporate authorship. See the reports at http://www.nlm.nih.gov/bsd/licensee/baselinestats.html and the summary in Figure 4.

The baseline data prepared near the end of calendar 2005 contain 13,673,101 citations of which:

15,012 citations have only corporate name authors
25,548 citations have both personal author(s) and corporate name author(s)

The majority of these 40,560 citations with corporate authors date from the year 2000 forward when NLM introduced the separate field for MEDLINE. Some, however, especially in the "only corporate name authors" category, are older citations that were converted from the specialty databases (such as the old POPLINE citations which had distinguished between personal and corporate authors earlier). The 40,560 citations have 43,304 occurrences of corporate authors, meaning that some citations have more than one corporate author.


Figure 4: Summary statistics for occurrence of Corporate Authors.


Note in Figure 4 that more citations have a mix of personal and corporate authors than only corporate authors. Many publishers and editors require a personal author in order to identify who is responsible for the integrity of the article. See the Council of Science Editors (CSE) and the International Committee of Medical Journal Editors (ICMJE) Web sites for more information about authorship.

By Lou Wave S. Knecht
Bibliographic Services Division

Knecht LS. Order of Authors in MEDLINE®/PubMed® Citations. NLM Tech Bull. 2006 May-Jun;(350):e2.