Perhaps you should try some spelling variations:
da literatura » la literatura, a literatura, de literatura
filosofia da » filosofia de, filosofia del, filosofia e
erste stufe » erster stufe
studien 3 » studien _, studien 5
studien 4 » studien _, studien 5

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: "erste stufe ((studien 3) OR (studien 4)) filosofia da literatura".
• Adding a wildcard symbol may retrieve word variants: erste stufe ((studien 3) OR (studien 4)) filosofia da literatura*.