Perhaps you should try some spelling variations:
da literature » a literature, da literatura, la literature
tests stable » tests table, sets stable, test table
filosofia da » filosofia de, filosofia del, filosofia e
studien es » studien aus, studien bei, studien ein
studien e » studien _, studien 3, studien 4

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 stable ((studien e) OR (studien es)) filosofia da literature.
• Adding a wildcard symbol may retrieve word variants: tests stable ((studien e) or (studien es)) filosofia da literature*.