Perhaps you should try some spelling variations:
la litterature » a literature
stable studies » table studies, unstable studies, scale studies
de filosofica » de filosofia, e filosofica, e filosofia
la literatura » a literature
tests stable » tests table, sets stable, test table
studies de » studies der, studies die, studies doe

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 studies de filosofica ((la literatura) OR (la litterature))*.