Perhaps you should try some spelling variations:
stable studien » stadler studien, scale studien, table studies
der filosofia » de filosofia, di filosofia, da filosofia
tests stable » tests table, sets stable, test table
y literatura » la literatura
e filosofia » la filosofia

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 ((der filosofia) OR (e filosofia)) y literatura.
• Adding a wildcard symbol may retrieve word variants: tests stable studien ((der filosofia) or (e filosofia)) y literatura*.