Perhaps you should try some spelling variations:
del litterature » de litterature, des litteratures, en litterature
et litterature » la litterature, art literature
case studies » case study
da filosofia » la filosofia, di filosofia, a 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: test ((wave studies) OR (case studies)) da filosofia ((del litterature) OR (et litterature)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "test ((wave studies) OR (case studies)) da filosofia ((del litterature) or (et litterature))".
• Adding a wildcard symbol may retrieve word variants: test ((wave studies) OR (case studies)) da filosofia ((del litterature) or (et litterature))*.