Container element for any series information used in a bibliographic reference (<citation>)
Within a citation to a non-journal item (for example, a book possibly spanning multiple volumes), the <series> element can contain the unique title of the entire series, as shown in the tagged example below. Similarly, some issues of journals are part of publishing series; within a bibliographic reference, this series information can be tagged using the <series> element.
<!ELEMENT series (#PCDATA %series-elements;)* >
Any combination of:
... <ref id="B1"><label>1</label> <citation citation-type="book"> <name><surname>...</surname></name> and <name><surname>...</surname></name>. <year>1989</year>. <series>The Birds of South America</series>. <volume>1</volume>. <source>The Oscine Passerines</source>. <publisher-name>University of Texas Press</publisher-name>, <publisher-loc>Austin</publisher-loc> </citation> </ref> ...