Perhaps you should try some spelling variations:
delphi studien » delphi studie, delphi study
delle studien » modell studien, welche studien, die studien
duale studien » duale studium, scale studien, duales studium
da literature » a literature, da literatura, la literature
filosofia da » filosofia de, filosofia del, filosofia e
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 (delphi studien))) OR (duale studien)) e filosofia da literature*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tesi ((((delle studien) OR (delphi studien))) or (duale studien)) e filosofia da literature*".