Perhaps you should try some spelling variations:
model literature » models literature, model literatur, modern literature
fuel literature » abel literature, level literature, novel literature
3 filosofia » e filosofia, a filosofia, y filosofia
studium 3 » studium _, studium 1, studium 8
test das » test des, test day, west das

You may be able to get more results by adjusting your search query.

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