Perhaps you should try some spelling variations:
de litterature » et litterature
la litterature » a literature
test duales » test doubles, test rules, test oracles
studium e » studium _, studium 3, studium 8
studium 1 » studium _, studium 3, studium 8

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 duales ((studium e) OR (studium 1)) filosofia ((de litterature) OR (la litterature)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "test duales ((studium e) OR (studium 1)) filosofia ((de litterature) or (la litterature))".
• Adding a wildcard symbol may retrieve word variants: test duales ((studium e) OR (studium 1)) filosofia ((de litterature) or (la litterature))*.