Perhaps you should try some spelling variations:
orale studien » duale studien, frage studien, scale studien
filosofia de » filosofia del
filosofia e » filosofia del
test orale » test oracle, test oral, test oracles
studien ds » studien des, studien das, studies ds

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: test orale studien ds ((filosofia e) OR (filosofia de)) literature.
• Adding a wildcard symbol may retrieve word variants: test orale studien ds ((filosofia e) or (filosofia de)) literature*.