Perhaps you should try some spelling variations:
der filosofica » e filosofica, e filosofia, di filosofia
da literatura » la literatura, a literatura, de literatura
de filosofia » e filosofia, di filosofia, la filosofia
drug studie » drug studies, drugs studies, drugs studied
tests drug » test drug, testing drug, tests during

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: "tests drug studie ((der filosofica) OR (de filosofia)) da literatura".
• Adding a wildcard symbol may retrieve word variants: tests drug studie ((der filosofica) OR (de filosofia)) da literatura*.