Perhaps you should try some spelling variations:
drugs studied » drugs studies, drug studies, groups studied
filosofica da » filosofia da, filosofia de, filosofia di
filosofica e » filosofia e, filosofia de, filosofia _
drug studie » drug studies, drugs studies, drug study

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: tests ((drug studie) OR (drugs studied)) 1 ((filosofica e) OR (filosofica da)) literatur.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tests ((drug studie) OR (drugs studied)) 1 ((filosofica e) or (filosofica da)) literatur".
• Adding a wildcard symbol may retrieve word variants: tests ((drug studie) OR (drugs studied)) 1 ((filosofica e) or (filosofica da)) literatur*.