[article Doc Title 1
[quickbook 1.5]
]

[/ Doc Titles for included files is a little odd. You generally don't see
   titles in them, the only way to detect them is through the generated ids.
   So that's what this test is for.
   
   The second include has a title, because that isn't scoped by file it will
   continue to be used to generated ids for the following included files -
   but not in this document as the document id for the file is generated
   for the whole file at the start.
   ]

[heading a1]

[include doc-title1-inc1.quickbook]

[heading a2]

[include doc-title1-inc2.quickbook]

[heading a3]

[include doc-title1-inc3.quickbook]

[heading a4]