Perhaps you should try some spelling variations:
del literatur » model literatur, teil literatur, igel literatur
der filosofia » de filosofia, e filosofia, di filosofia
studies der » studies ds, studies d, studies dn
wet gels » wet gas

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: ((wet gels) OR (wet gel)) studies der filosofia del literatur.
• Adding a wildcard symbol may retrieve word variants: ((wet gels) or (wet gel)) studies der filosofia del literatur*.