Perhaps you should try some spelling variations:
da literature » a literature, da literatura, la literature
filosofia da » filosofia de, filosofia del, filosofia e
tests scale » tests stable, sets scale, tests safe
studien ein » studien eine, studieren ein, studien die
studien e » studien es, studien _, studien 3

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 scale ((studien e) OR (studien ein)) filosofia da literature.
• Adding a wildcard symbol may retrieve word variants: tests scale ((studien e) or (studien ein)) filosofia da literature*.