The volume number of this book within the described collection.
<!ELEMENT volume-number (#PCDATA %volume-number-elements;)* >
(#PCDATA | sub | sup)*
...
<collection-meta>
<title-group>
<title>Balisage Series on Markup Technologies</title>
</title-group>
<volume-in-collection>
<volume-number>10</volume-number>
<volume-title>Proceedings of Balisage: The Markup Conference
2013</volume-title>
</volume-in-collection>
<issn>1947-2609</issn>
<publisher>
<publisher-name>Mulberry Technologies, Inc.</publisher-name>
</publisher>
<abstract>
<p>The <italic>Balisage Series on Markup Technologies</italic>
is an occasional series that includes the proceedings of
conferences, symposia, and other markup-related events.</p>
</abstract>
</collection-meta>
...