Perhaps you should try some spelling variations:
"nijhoff book title 21" » "nijhoff boston title 21", "nijhoff book titles 21", "nijhoff ebook title 21", "nijhoff book table 21", "nijhoff book title 1", "nijhoff book title 2", "nijhoff book title _"
"nijhoff op title 25" » "nijhoff _ title 25", "nijhoff j title 25", "nijhoff sop title 25", "nijhoff shop title 25", "nijhoff app title 25", "nijhoff op title 2", "nijhoff op title 5", "nijhoff op title 26"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("nijhoff op title 25") OR ("nijhoff book title 21")).
• Removing quotes may allow a broader search: (( nijhoff op title 25 ) or ( nijhoff book title 21 )).
• Adding a wildcard symbol may retrieve word variants: (("nijhoff op title 25") or ("nijhoff book title 21"))*.