Perhaps you should try some spelling variations:
testing drug » testing during, testing data
drug studie » drug studies, drugs studies, drugs studied
a filosofia » e filosofia, di filosofia
literatur » literature

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: testing drug studie ((a filosofia) OR (la filosofia)) e literatur.
• Adding a wildcard symbol may retrieve word variants: testing drug studie ((a filosofia) or (la filosofia)) e literatur*.