Number of a journal (or other document) within its series
The <volume> element is used in two contexts: 1) as a part of the metadata describing a book itself, and 2) as part of a description of a cited work inside a bibliographic reference (<citation>).
<!ELEMENT volume (#PCDATA %volume-elements;)* >
Any combination of:
<book-meta> Book Metadata; <book-part-meta> Book Part Metadata; <citation> Citation; <related-article> Related Article Information
...<ref-list>
<title>References</title>
<ref id="bid.41">
<label>1</label>
<citation>
<person-group>
<name><surname>Olson</surname><given-names>M</given-names></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>
</citation>
</ref>
</ref-list>...
common.ent