Perhaps you should try some spelling variations:
del litterature » de litterature, des litteratures, et litterature
y filosofia » e filosofia, a filosofia, la filosofia
besten der » bestehen der, bestimmen der, bestehens der
beste oder » beste der, beute oder, werte oder
studie y » studie 2, studie _, studie 1

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: ((besten der) OR (beste oder)) studie y filosofia del litterature.
• Adding a wildcard symbol may retrieve word variants: ((besten der) or (beste oder)) studie y filosofia del litterature*.