Perhaps you should try some spelling variations:
"nijhoff book titles 2006" » "nijhoff boston titles 2006", "nijhoff op titles 2006", "nijhoff book entitled 2006", "nijhoff book intitled 2006"
"nijhoff ebook title 20" » "nijhoff book title 20", "nijhoff ebook title 2", "nijhoff ebook title 10", "nijhoff ebook title 21"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"nijhoff book titles 2006\") OR (\"nijhoff ebook title 20\"))".
• Removing quotes may allow a broader search: (( nijhoff book titles 2006 ) OR ( nijhoff ebook title 20 )).
• Adding a wildcard symbol may retrieve word variants: (("nijhoff book titles 2006") OR ("nijhoff ebook title 20"))*.