<book> --> <part>

Sda1/sda1.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<book xml:id="sda1" 
+<part xml:id="sda1" 
       version="5.0" xmlns="http://docbook.org/ns/docbook"
       xmlns:xlink="http://www.w3.org/1999/xlink"
       xmlns:xi="http://www.w3.org/2001/XInclude"
@@ -13982,4 +13982,4 @@ leader-pattern="dots"/&gt;C&lt;fo:leader leader-pattern="dots"/&gt;D&lt;/fo:bloc
   </appendix>
   <xi:include href="../bibliography.xml" xpointer="element(/1)"/>
-</book>
+</part>