Perhaps you should try some spelling variations:
del litterature » de litterature, des litteratures, et litterature
ds filosofia » di filosofia, de filosofia, da filosofia
2dg studies » fdg studies, eeg studies, g studies
dg studies » fdg studies, g studies, drug studies

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 ((2dg studies) OR (dg studies)) ds filosofia del litterature".
• Adding a wildcard symbol may retrieve word variants: test ((2dg studies) OR (dg studies)) ds filosofia del litterature*.