Perhaps you should try some spelling variations:
dualen studium » duales studium, duale studium
di filosofia » la filosofia, e filosofia
a filosofia » la filosofia, e filosofia
des dualen » der dualen, des idealen

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: "des dualen studium ((a filosofia) OR (di filosofia)) a literature".
• Adding a wildcard symbol may retrieve word variants: des dualen studium ((a filosofia) OR (di filosofia)) a literature*.