Perhaps you should try some spelling variations:
"nijhoff boston titles 21" » "nijhoff boston tables 21", "nijhoff boston times 21", "nijhoff boston entitled 21", "nijhoff boston titles 1", "nijhoff boston titles 11", "nijhoff boston titles 71"
"nijhoff book titles 21" » "nijhoff op titles 21", "nijhoff book entitled 21", "nijhoff book intitled 21", "nijhoff book tables 21", "nijhoff work titles 21", "nijhoff book times 21", "nijhoff book titles 1", "nijhoff book titles 11", "nijhoff book titles 71"
"nijhoff book title 26" » "nijhoff op title 26", "nijhoff book table 26", "nijhoff work title 26", "nijhoff book time 26", "nijhoff book title 2", "nijhoff book title 21", "nijhoff book title 25"
"nijhoff ebook title 2006" » "nijhoff ebook title 20", "nijhoff ebook title 2012", "nijhoff ebook table 2006", "nijhoff ework title 2006", "nijhoff ebook time 2006"
"nijhoff ebola time 2006" » "nijhoff ebola time 2000", "nijhoff ebola time 2001", "nijhoff ebola time 2004"

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 ebook title 2006\") OR (\"nijhoff ebola time 2006\"))) OR (((((\"nijhoff book titles 21\") OR (\"nijhoff boston titles 21\"))) OR (\"nijhoff book title 26\"))))".
• Removing quotes may allow a broader search: (((( nijhoff ebook title 2006 ) OR ( nijhoff ebola time 2006 ))) OR ((((( nijhoff book titles 21 ) OR ( nijhoff boston titles 21 ))) OR ( nijhoff book title 26 )))).
• Adding a wildcard symbol may retrieve word variants: (((("nijhoff ebook title 2006") OR ("nijhoff ebola time 2006"))) OR ((((("nijhoff book titles 21") OR ("nijhoff boston titles 21"))) OR ("nijhoff book title 26"))))*.