Perhaps you should try some spelling variations:
fuel literature » abel literature, level literature, model literature
des studium » des studiums, das studium, dem studium
a filosofia » la filosofia, di filosofia
e filosofia » la filosofia
test des » test der, test test

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 des studium ((a filosofia) OR (e filosofia)) fuel literature".
• Adding a wildcard symbol may retrieve word variants: test des studium ((a filosofia) OR (e filosofia)) fuel literature*.