Perhaps you should try some spelling variations:
die filosofica » de filosofia, e filosofica, vida filosofica
tests stable » tests table, sets stable, test table
di filosofia » la filosofia, e filosofia
a literatura » la literatura, a literature, y literatura
tests safe » tests safety, tests scale, tests space

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)) studies ((die filosofica) OR (di filosofia)) a literatura.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tests safe) or (tests stable)) studies ((die filosofica) OR (di filosofia)) a literatura".
• Adding a wildcard symbol may retrieve word variants: ((tests safe) or (tests stable)) studies ((die filosofica) OR (di filosofia)) a literatura*.