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book-type Type of Book

Type or kind of book, for example, a technical monograph, government report, volume of a monographic series, STM reference work, etc.
OPTIONAL on element: <book>
Value Meaning
Text, numbers, or special characters Names the type of book, for example, “gov” for a government report.
Restriction @book-type is an optional attribute; there is no default.
Tagged Sample

Government report

<book
  xmlns:mml="http://www.w3.org/1998/Math/MathML"
  xmlns:xi="http://www.w3.org/2001/XInclude"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  book-type="gov"
  dtd-version="2.1"
  indexed="yes"
  xml:lang="en">
 <book-meta>...</book-meta>
 <book-body>...</book-body>
 <book-back>...</book-back>
</book>