Used to mark unstructured text within an otherwise element-structured bibliographic reference (<nlm-citation>); it is therefore not necessarily a comment in the formal sense of commentary. In an unstructured bibliographic reference, this text would merely be a mixture of text, numbers, or special characters, such as punctuation, and not marked with tags at all.
The element <comment> is used to contain additional information about a citation that is not appropriate in any of the other, named, information types. For extensive examples of formatted <nlm-citation>s including use of <comment>s in <nlm-citation>s, see: Sample PubMed Central Citations. To see tagged versions of these example, see: Sample PubMed Central Citations - XML Tagged.
Because the model for <citation> is a loose model with data characters allowed everywhere, this element will rarely be needed in <citation>s. The <comment> element is used in <citation>s largely for the sake of conversion, to preserve unusual bits of semantic markup when translating from other DTDs. Typical comments might include:
<comment>[Abstract]</comment> <comment>translated from Russian</comment>
Conversion Note: The <comment> element should be used to mark substantive text only; it should not be used to markup punctuation that occurs between elements.
<!ELEMENT comment (#PCDATA %comment-elements;)* >
Any combination of:
... <ref> <nlm-citation citation-type="book"> <person-group person-group-type="author"> <name> <surname>McRae</surname> <given-names>Jackie</given-names> </name> </person-group> <source>AIDS, agencies and drug abuse: the Edinburgh experience</source> <year>1989</year> <publisher-loc>Norwich (England)</publisher-loc> <publisher-name>Social Works Monographs</publisher-name> <lpage>40</lpage> <comment>Revised version of a dissertation originally submitted as part of an MSc. in applied social studies at Oxford University</comment> </nlm-citation></ref> ...