Perhaps you should try some spelling variations:
di filosofia » la filosofia, e filosofia
de filosofia » e filosofia, la filosofia, a filosofia
drug studie » drug studies, drugs studies, drugs studied
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 studie ((de filosofia) OR (di filosofia)) a literature".
• Adding a wildcard symbol may retrieve word variants: test drug studie ((de filosofia) OR (di filosofia)) a literature*.