Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
studies die » studie die, studien die, studies does
test scale » tests scale, best scale, rest scale
studies de » studies der, studies doe, studies due

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 scale ((studies de) OR (studies die)) filosofia del literatura".
• Adding a wildcard symbol may retrieve word variants: test scale ((studies de) OR (studies die)) filosofia del literatura*.