Perhaps you should try some spelling variations:
duale studien » duale studium, scale studien, duales studium
filosofia de » filosofia del
filosofia e » filosofia del
studien es » studien aus, studien bei, studien ein

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