Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
di filosofia » la filosofia, e filosofia
best drugs » obesity drugs
test drug » tests drug, test du, fast drug
studie di » studie die, studie d, studie 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: "((test drug) OR (best drugs)) studie di filosofia del literatura".
• Adding a wildcard symbol may retrieve word variants: ((test drug) OR (best drugs)) studie di filosofia del literatura*.