Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
studien des » studien der, studie des, studien aus
studien de » studien der, studien die, studien dd
test oral » test oracle, test orn, test oracles

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 oral ((studien de) OR (studien des)) filosofia del literatura*.