Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
duales studium » das studium
duale studien » duale studium, scale studien, dualen studium
de filosofia » e filosofia, di filosofia, la filosofia

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: "tests ((duale studien) OR (duales studium)) de filosofia del literatura".
• Adding a wildcard symbol may retrieve word variants: tests ((duale studien) OR (duales studium)) de filosofia del literatura*.