Perhaps you should try some spelling variations:
test modell » tekst modell, test models, test model
studien des » studien der, studie des, studien aus
filosofia e » filosofia de, filosofia del
e literatur » die literatur
studien ds » studien das, studies ds, studien dd

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 ds) OR (studien des)) filosofia e literatur".
• Adding a wildcard symbol may retrieve word variants: test modell ((studien ds) OR (studien des)) filosofia e literatur*.