Perhaps you should try some spelling variations:
del literatur » model literatur, teil literatur, igel literatur
test duales » test doubles, test rules, test oracles
studium la » studium als, studium das, studium _
studium a » studium am, studium ad, studium _

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 duales ((studium la) OR (studium a)) filosofia del literatur".
• Adding a wildcard symbol may retrieve word variants: test duales ((studium la) OR (studium a)) filosofia del literatur*.