Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
studies die » studien die, studies does, studies dose
studies de » studies der, studies doe, studies due
studie die » studie der
test gels » test goals, test get, wet gels

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 gels ((studies de) OR (((studies die) OR (studie die)))) filosofia del literatura.
• Adding a wildcard symbol may retrieve word variants: test gels ((studies de) or (((studies die) or (studie die)))) filosofia del literatura*.