Perhaps you should try some spelling variations:
y filosofica » y filosofia, e filosofica, y filosoficos
y filosofico » y filosoficos, y filosofia, e filosofica
auf studium » fur studium, zum studium, als studium
eu studies » 2 studies, 3 studies, 5 studies
zu studie » zu studien, zu studium, zu stufe

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 ((((zu studie) OR (eu studies))) OR (auf studium)) ((y filosofica) OR (y filosofico)) a literature*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "test ((((zu studie) or (eu studies))) or (auf studium)) ((y filosofica) OR (y filosofico)) a literature*".