Perhaps you should try some spelling variations:
"nijhoff boston entitled 60" » "nijhoff boston entituled 60", "nijhoff boston entitled 10", "nijhoff boston entitled _", "nijhoff boston entitled a"
"nijhoff book entitled 2006" » "nijhoff book entitled 10", "nijhoff op entitled 2006"
"nijhoff book untitled 2001" » "nijhoff book intitled 2001", "nijhoff book entituled 2001", "nijhoff book intituled 2001", "nijhoff book untitled 2", "nijhoff op untitled 2001"

Try widening your search to All Fields.

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 book entitled 2006") OR ("nijhoff book untitled 2001"))) OR ("nijhoff boston entitled 60")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"nijhoff book entitled 2006\") OR (\"nijhoff book untitled 2001\"))) or (\"nijhoff boston entitled 60\"))".
• Removing quotes may allow a broader search: (((( nijhoff book entitled 2006 ) OR ( nijhoff book untitled 2001 ))) or ( nijhoff boston entitled 60 )).
• Adding a wildcard symbol may retrieve word variants: (((("nijhoff book entitled 2006") OR ("nijhoff book untitled 2001"))) or ("nijhoff boston entitled 60"))*.