Perhaps you should try some spelling variations:
"nijhoff op untitled 2001" » "nijhoff op untitled 2", "nijhoff 1 untitled 2001", "nijhoff 3 untitled 2001", "nijhoff 10 untitled 2001", "nijhoff _ untitled 2001", "nijhoff j untitled 2001"
"nijhoff book titles 2006" » "nijhoff boston titles 2006", "nijhoff book entitled 2006", "nijhoff book intitled 2006"

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 op untitled 2001\"))".
• Removing quotes may allow a broader search: (( nijhoff book titles 2006 ) OR ( nijhoff op untitled 2001 )).
• Adding a wildcard symbol may retrieve word variants: (("nijhoff book titles 2006") OR ("nijhoff op untitled 2001"))*.