Perhaps you should try some spelling variations:
la litterature » a literature
la literatura » a literature
tests safe » tests safety, tests scale, tests space
studie der » studium der

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: tests safe ((studie die) OR (studie der)) filosofica ((la literatura) OR (la litterature)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tests safe ((studie die) or (studie der)) filosofica ((la literatura) OR (la litterature))".
• Adding a wildcard symbol may retrieve word variants: tests safe ((studie die) or (studie der)) filosofica ((la literatura) OR (la litterature))*.