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

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