Some citations are complicated by the fact that they do not provide the full citation information for each cited reference. For example, some journals identify successive bibliographic references by the same author or involving the same journal by omitting the duplicated portion of the reference and inserting a vertical rule, the word “Ibid”, the word “Id.”, etc. Other publishers routinely omit the title of a cited journal article to save space. While best practice is to tag all citations completely, archives or publishers may choose to tag an abbreviated citation exactly as it was displayed.
If it is important for an archive or publisher to make each citation accessible for citation matching services, incomplete references should be enhanced by tagging the missing information based on the preceding reference. At the discretion of the archive, the word “Ibid” or “Id.” may also be retained as part of the textual content.
As an example, here is a citation that mixes multiple works by a single author:
Holmes, S. J. (1) Phototaxis in the amphipoda. Am. Jour. Physiol., 5, 211, 1901; (2) The reactions of Ranatra to light. Jour. Comp. Neur. Psych., 15, 305, 1905.
To preserve the exact order and punctuation of these citations, each publisher or archive must decide whether the semicolon and space between the citations is part of the first citation or the second. Here is the double-citation reference tagged as a mixed-style citation, with the punctuation added to the end of the first citation:
<ref id="ref1" content-type="double-author"> <mixed-citation publication-type="journal"> <string-name> <surname>Holmes</surname>, <given-names>S.J.</given-names> </string-name> <label>(1)</label> <article-title>Phototaxis in the amphipoda</article-title>. <source>Am. Jour. Physiol.</source>, <volume>5</volume>, <issue>211 </issue>, <year>1901</year>; </mixed-citation> <mixed-citation><label>(2)</label> <article-title>The reactions of Ranatra to light</article-title>. <source>Journ. Comp. Neur. Physch.</source>, <volume>15</volume>, <issue>305</issue>, <year>1905</year>. </mixed-citation> </ref>
If completeness of citations for reference matching is more important than preserving the original word order and exact punctuation, information that is only displayed in one citation should be tagged in both. Because display is less important than completeness, the label can be moved to the beginning of the citation. Here is the same citation tagged as an element-style citation and incorporating the changes just mentioned:
<ref id="ref1" content-type="double-author"> <element-citation publication-type="journal"> <label>(1)</label> <name><surname>Holmes</surname><given-names>S.J.</given-names></name> <article-title>Phototaxis in the amphipoda</article-title> <source>Am. Jour. Physiol.</source> <volume>5</volume><issue>211</issue><year>1901</year> </element-citation> <element-citation> <label>(2)</label> <name><surname>Holmes</surname><given-names>S.J.</given-names></name> <article-title>The reactions of Ranatra to light</article-title> <source>Journ. Comp, Neur. Physch.</source> <volume>15</volume><issue>305</issue><year>1905</year> </element-citation> </ref>