Perhaps you should try some spelling variations:
e literatura » de literatura, y literatura, e literatur
studium des » studium der
filosofia e » filosofia de, filosofia del
tests drug » test drug, testing drug, tests during
studie des » studie der, studie die

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 des) OR (studium des)) filosofia e literatura.
• Adding a wildcard symbol may retrieve word variants: tests drug ((studie des) or (studium des)) filosofia e literatura*.