Perhaps you should try some spelling variations:
delle studien » delphi studien, modell studien, welche studien
duale studien » duale studium, scale studien, duales studium
de literature » de litterature, de lite'rature, de literatura
filosofia de » filosofia del
e filosofia » la filosofia

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: tesi ((delle studien) OR (duale studien)) e filosofia de literature*.