Perhaps you should try some spelling variations:
model studien » modell studien, model studies, models studies
filosofia da » filosofia del, filosofia e, filosofia della
filosofia de » filosofia del
test model » test models, trust model, cost model
studien am » studien a, studien aus, studien auf

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