Perhaps you should try some spelling variations:
a literatura » la literatura, a literature, y literatura
filosofia a » filosofia da, filosofia la, filosofia e
tests drug » test drug, testing drug, tests during
studie die » studie der
studie de » studie der, studie des, studies de

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 de) OR (studie die)) filosofia a literatura*".