Perhaps you should try some spelling variations:
la literatura » la litterature, a literature
tests stable » tests table, sets stable, test table
dd filosofia » di filosofia, de filosofia, da filosofia
filosofia la » filosofia da, filosofia le, filosofica da
tests scale » sets scale, tests safe, tests shall
studien dd » studies dd, studien der, studien die

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 scale) OR (tests stable)) studien dd filosofia la literatura.
• Adding a wildcard symbol may retrieve word variants: ((tests scale) or (tests stable)) studien dd filosofia la literatura*.