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issue Issue Number of a Related Article

Issue number of a journal which contains the related article.

Usage/Remarks

The @issue attribute can be used, along with the @vol, @journal-id, and @page attributes, to provide the metadata for the related article.
OPTIONAL on element: <related-article>
Value Meaning
Text, numbers, or special characters The number of the journal issue, such as “48”.
Restriction @issue is an optional attribute; there is no default.
Tagged Sample

Giving the issue number for an Addendum (a <related-article>) 

...
<related-article elocation-id="052207" ext-link-type="uri"
  related-article-type="addendum" xlink:href="7596428"
  journal-id="MULB" journal-id-type="publisher-id" vol="281"
  issue="318" page="582"/>
...