Issue number of a journal, or in rare instances, a book.
In Citations: In this Tag Set, article-related issue numbers are only used in citations and other elements that describe publications. For example, the <issue> element is used in bibliographic references (<element-citation> and <mixed-citation>) where it indicates the issue in which the cited material was published.
In Joint Issues: If an article was published in a joint issue “Iss. 2-3”, both issue numbers should be placed into a single <issue> element: <issue>1-2</issue>. In citations, this circumstance is very rare.
Multiple Issue Numbers: The element issue number (<issue>) is allowed to repeat, to handle the rare circumstance in which a publisher has both an issue number within a volume and an issue sequence number (not volume related) within the run of the publication. In such cases, the attribute @content-type should be used to differentiate the two types of issues.
As an example from an 1897 journal of the Boston Society of Medical Sciences, the “Vol.” was given as “II”, the “No.” as “1”, and the “Whole No.” as “17”. (See Cover: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2121746 and Article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2121742/.)
As another example from the Journal of Medical Research in 1902, the Vol. was given as “VIII”, the “No.” as “2”, and the “Whole No.” as “70”. (See Cover: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2105871/ and Article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2105865/.)
<!ELEMENT issue (#PCDATA %issue-elements;)* >
(#PCDATA | email | ext-link | uri | inline-supplementary-material | related-article | related-object | hr | bold | fixed-case | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | strike | underline | underline-start | underline-end | ruby | alternatives | inline-graphic | private-char | chem-struct | inline-formula | tex-math | mml:math | abbrev | index-term | index-term-range-end | milestone-end | milestone-start | named-content | styled-content | fn | target | xref | sub | sup | x)*
Any combination of:
<element-citation>, <mixed-citation>, <product>, <related-article>, <related-object>
In an element-style bibliographic reference (punctuation and spacing removed):
...
<ref>
<element-citation publication-type="journal" publication-format="print">
<name><surname>Llanos De La Torre Quiralte</surname>
<given-names>M</given-names></name>
<name><surname>Garijo Ayestaran</surname>
<given-names>M</given-names></name>
<name><surname>Poch Olive</surname>
<given-names>ML</given-names></name>
<article-title xml:lang="es">Evolucion de la mortalidad
infantil de La Rioja (1980-1998)</article-title>
<trans-title xml:lang="en">Evolution of the infant
mortality rate in la Rioja in Spain
(1980-1998)</trans-title>
<source>An Esp Pediatr</source>
<year iso-8601-date="2001-11">2001</year>
<month>Nov</month>
<volume>55</volume>
<issue>5</issue>
<fpage>413</fpage>
<lpage>420</lpage>
<comment>Figura 3, Tendencia de mortalidad infantil
[Figure 3, Trends in infant mortality]; p. 418.
Spanish</comment>
</element-citation>
</ref>
...
In a mixed-style bibliographic reference (punctuation and spacing preserved):
...
<ref>
<mixed-citation publication-type="journal" publication-format="print">
<string-name><surname>Llanos De La Torre Quiralte</surname>
<given-names>M</given-names></string-name>,
<string-name><surname>Garijo Ayestaran</surname>
<given-names>M</given-names></string-name>,
<string-name><surname>Poch Olive</surname>
<given-names>ML</given-names></string-name>.
<article-title xml:lang="es">Evolucion de la mortalidad
infantil de La Rioja (1980-1998)</article-title>
[<trans-title xml:lang="en">Evolution of the infant
mortality rate in la Rioja in Spain
(1980-1998)</trans-title>]. <source>An Esp Pediatr</source>.
<year iso-8601-date="2001-11">2001</year>
<month>Nov</month>;<volume>55</volume>(<issue>5</issue>):
<fpage>413</fpage>-<lpage>420</lpage>. Figura 3, Tendencia
de mortalidad infantil [Figure 3, Trends in infant
mortality]; p. 418. Spanish.</mixed-citation>
</ref>
...