Perhaps you should try some spelling variations:
duale studien » duale studium, scale studien, duales studium
ein filosofia » e filosofia, di filosofia, en filosofie
de literatura » de litterature, la literatura, y literatura
testo » test, tests, texto

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: testo duale studien ((ein filosofia) OR (la filosofia)) de literatura*.