Records the total number of either a) the references (<ref>) or (more properly) b) the number of citations (<mixed-citation>) that appear in the bibliographic reference list (<ref-list>) for a book. This count is (roughly) the number of sources cited in the book.
The count elements are modeled as EMPTY elements that have no content but carry values on their attributes.
<!ELEMENT ref-count EMPTY >
This is an EMPTY element
<book> <book-meta> <book-id pub-id-type="other">handbook</book-id> <book-title-group> <book-title>The NCBI Handbook</book-title> </book-title-group>... <counts> <fig-count count="98"/> <table-count count="40"/> <equation-count count="0"/> <ref-count count="115"/> <page-count count="532"/> <word-count count="149852"/> </counts> </book-meta> <book-front>...</book-front> <body>...</body> <back>...</back> </book>