International Standard Serial Number, the international code that uniquely identifies a serial publication title.
<!ELEMENT issn (#PCDATA %issn-elements;)* >
(#PCDATA | x)*
Any combination of:
<book-meta>, <book-part-meta>, <collection-meta>, <element-citation>, <event>, <event-desc>, <mixed-citation>, <product>, <related-article>, <related-object>
In an element-style bibliographic reference (punctuation and spacing removed):
...
<ref>
<element-citation>
<person-group person-group-type="author">
<name><surname>Forster</surname>
<given-names>Anne Williams</given-names></name>
<name><surname>Young</surname>
<given-names>John G.</given-names></name>
</person-group>
<article-title>Systematic review of day hospital
care for elderly people</article-title>
<source>British Medical Journal</source>
<volume>318</volume>
<issue>7187</issue>
<fpage>837</fpage>
<lpage>841</lpage>
<day>27</day>
<month>03</month>
<year iso-8601-date="1999">1999</year>
<issn>0959-8138</issn>
<pub-id>10092260</pub-id>
</element-citation>
</ref>
...
In a mixed-style bibliographic reference (punctuation and spacing preserved):
...
<ref>
<mixed-citation>
<person-group person-group-type="author">
<string-name><surname>Forster</surname>
<given-names>Anne Williams</given-names></string-name>
<string-name><surname>Young</surname>
<given-names>John G.</given-names></string-name>
</person-group>.
<article-title>Systematic review of day hospital
care for elderly people</article-title>.
<source>British Medical Journal</source>.
<day>27</day> <month>03</month>
<year iso-8601-date="1999">1999</year>;
<volume>318</volume>(<issue>7187</issue>):
<fpage>837</fpage>–<lpage>841</lpage>.
ISSN: <issn>0959-8138</issn>.
<pub-id>10092260</pub-id>.
</mixed-citation>
</ref>
...
JATS-common1.ent