Perhaps you should try some spelling variations:
pela literatura » pena literatura, a literatura, de literatura
la literatura » la litterature, a literature
drug studie » drug studies, drugs studies, drugs studied
tests drug » test drug, testing drug, tests during
studie la » studie a, studie lp, studiare la

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 la filosofia ((pela literatura) OR (la literatura))*".