The identifier of a publication, such as a journal article, that is listed within a <mixed-citation> inside a book or book component’s <ref-list>
The @pub-id-type attribute is used either to identify the type of identifier, or to name the authority, organization, or system that defined this identifier, for example identifying a DOI, PubMed Central identifier, PII, the publisher’s identifier, etc. (See @pub-id-type for values.)
<!ELEMENT pub-id (#PCDATA) >
Text, numbers, or special characters
<element-citation>, <mixed-citation>, <nlm-citation>, <product>, <related-article>, <related-object>
In an element-style bibliographic reference (punctuation and spacing removed):
...
<ref id="bid.41">
<label>1</label>
<element-citation >
<person-group>
<string-name><surname>Olson</surname>
<given-names>M</given-names></string-name>
<string-name><surname>Hood</surname>
<given-names>L</given-names></string-name>
<string-name><surname>Cantor</surname>
<given-names>C</given-names></string-name>
<string-name><surname>Botstein</surname>
<given-names>D</given-names></string-name>
</person-group>
<article-title>A common language for physical mapping
of the human genome</article-title>
<source>Science</source>
<year>1989</year>
<volume>245</volume>
<issue>4925</issue>
<fpage>1434</fpage>
<lpage>1435</lpage>
<pub-id pub-id-type="pmid">2781285</pub-id>
</element-citation>
</ref>
</ref-list>
</back>
</book-part>
...
In a mixed-style bibliographic reference (punctuation and spacing preserved):
...
<ref-list>
<title>References</title>
<ref id="B8"><label>8</label>
<mixed-citation>
<string-name><surname>Weissert</surname>
<given-names>W</given-names></string-name>,
<string-name><surname>Wan</surname>
<given-names>T</given-names></string-name>,
<string-name><surname>Livieratos</surname>
<given-names>B</given-names></string-name>,
<string-name><surname>Katz</surname>
<given-names>S</given-names></string-name>.
<article-title>Effects and costs of day-care services
for the chronically ill: a randomized experiment</article-title>.
<source>Medical Care</source>
<year>1980</year>;
<volume>18</volume>:
<fpage>567</fpage>–
<lpage>584</lpage>.
<pub-id pub-id-type="pmid">6772889</pub-id>.
</mixed-citation>
</ref>
...
references3.ent