Perhaps you should try some spelling variations:
del literature » model literature, abel literature, fuel literature
des filosofia » de filosofia, e filosofia, di filosofia
tests duale » tests scale, tests damage
studium des » studium der
tests due » tests die, tests de, tests drug

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: "((tests duale) OR (tests due)) studium des filosofia del literature".
• Adding a wildcard symbol may retrieve word variants: ((tests duale) OR (tests due)) studium des filosofia del literature*.