Perhaps you should try some spelling variations:
le literatura » la literatura, de literatura, e literatura
tests stable » tests table, sets stable, test table
filosofia le » filosofia de, filosofia e, filosofia del
tests safe » tests safety, tests scale, tests space
study la » study law, study lay, study lca

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 safe) OR (tests stable)) study la filosofia le literatura.
• Adding a wildcard symbol may retrieve word variants: ((tests safe) or (tests stable)) study la filosofia le literatura*.