Perhaps you should try some spelling variations:
"nijhoff work title _6" » "nijhoff op title _6", "nijhoff work time _6", "nijhoff work entitled _6", "nijhoff work intitled _6", "nijhoff work title _", "nijhoff work title 26", "nijhoff work title 16"
"nijhoff ebook title 2006" » "nijhoff book title 2006", "nijhoff book titles 2006", "nijhoff ebook title 26", "nijhoff ebook title 20", "nijhoff ebook title 2012", "nijhoff ebook title _006", "nijhoff ebook title a006", "nijhoff ebook title 1006"
"nijhoff ebook title 2" » "nijhoff book title 2", "nijhoff book titles 2", "nijhoff ebook title _", "nijhoff ebook title a", "nijhoff ebook title 1"

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 work title _6\") OR (\"nijhoff ebook title 2\"))))*".
• Removing quotes may allow a broader search: (( nijhoff ebook title 2006 ) OR ((( nijhoff work title _6 ) OR ( nijhoff ebook title 2 ))))*.