Perhaps you should try some spelling variations:
de literatura » de litterature, la literatura, y literatura
filosofia de » filosofia del
studien des » studie des, studien aus, studien die
studien der » studie der, studenten der

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 OR tests) duale ((studien des) OR (studien der)) filosofia de literatura.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(testo or tests) duale ((studien des) OR (studien der)) filosofia de literatura".
• Adding a wildcard symbol may retrieve word variants: (testo or tests) duale ((studien des) OR (studien der)) filosofia de literatura*.