Perhaps you should try some spelling variations:
da litterature » la litterature, de litterature, a litterature
delphi studien » delphi studie, delphi study
de filosofia » e filosofia, la filosofia, a filosofia
di filosofia » la filosofia, e filosofia
test delphi » fast delphi, belts delphi

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "test delphi studien ((de filosofia) OR (di filosofia)) da litterature".
• Adding a wildcard symbol may retrieve word variants: test delphi studien ((de filosofia) OR (di filosofia)) da litterature*.