Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
drugs studies » drug studies
di filosofia » la filosofia, e filosofia
drug studie » drug studies, drugs studied, drug study

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: "test ((drug studie) OR (drugs studies)) di filosofia del literatura".
• Adding a wildcard symbol may retrieve word variants: test ((drug studie) OR (drugs studies)) di filosofia del literatura*.