The issue number of a journal; in the journal metadata, this is the issue number of the issue in which the article appears.
<!ELEMENT issue (#PCDATA %issue-elements;)* >
Any combination of:
<article-meta> Article Metadata; <citation> Citation; <product> Product Information; <related-article> Related Article Information
...
<article-meta>
<article-id pub-id-type="pmid">...</article-id>
<title-group>...</title-group>
<contrib-group>...</contrib-group>
<aff id="StLukes">...</aff>
<pub-date pub-type="pub">
<day>27</day><month>03</month>
<year>1999</year>
</pub-date>
<volume>318</volume>
<issue>7187</issue>
<fpage>837</fpage>
<lpage>841</lpage>
<history>
<date date-type="accepted">
<day>29</day>
<month>01</month>
<year>1999</year></date>
</history>
<permissions>
<copyright-statement>Copyright © 1999, British
Medical Journal</copyright-statement>
<copyright-year>1999</copyright-year>
<copyright-holder>British Medical Journal</copyright-holder>
</permissions>
<abstract>
<p>To examine the effectiveness of day hospital
attendance in prolonging independent living for
elderly people.</p>
</abstract>
</article-meta>
...
common.ent