Perhaps you should try some spelling variations:
la literatura » la litterature, a literature
filosofia la » filosofia da, filosofia le, filosofica da
test modell » tekst modell, test models, test model
studien am » studien aus, studien auf, studien _
studien a » studien _, studien 3, studien 4

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 modell ((studien am) OR (studien a)) filosofia la literatura".
• Adding a wildcard symbol may retrieve word variants: test modell ((studien am) OR (studien a)) filosofia la literatura*.