Perhaps you should try some spelling variations:
pela literatura » pena literatura, la literatura, a literatura
del literatura » de literatura, da literatura, e literatura
der filosofia » de filosofia, e filosofia, di filosofia
studies der » studies ds, studies d, studies dn
test drug » tests drug, best drugs, test du

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: "test drug studies der filosofia ((del literatura) OR (pela literatura))".
• Adding a wildcard symbol may retrieve word variants: test drug studies der filosofia ((del literatura) OR (pela literatura))*.