The title of the book in the language in which the book was originally published
<!ELEMENT book-title (#PCDATA %title-elements;)* >
Any combination of:
<book>
<book-meta>
<book-id pub-id-type="other">emdocrin</book-id>
<book-title-group>
<book-title>Endocrinology</book-title>
<subtitle>An Integrated Approach</subtitle>
</book-title-group>
...</book-meta>
<book-front>...</book-front>
<body>...</body>
<back>...</back>
</book>
bookmeta.ent