Perhaps you should try some spelling variations:
model literature » models literature, model literatur, modern literature
del literature » abel literature, fuel literature, al literature
studium 3 » studium 1, studium im
studium 8 » studium 1, studium im
test des » test der, test test

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: test des ((((studium 3) OR (studium _))) OR (studium 8)) filosofia ((del literature) OR (model literature)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "test des ((((studium 3) or (studium _))) or (studium 8)) filosofia ((del literature) OR (model literature))".
• Adding a wildcard symbol may retrieve word variants: test des ((((studium 3) or (studium _))) or (studium 8)) filosofia ((del literature) OR (model literature))*.