Perhaps you should try some spelling variations:
e literature » life literature, prose literature, norse literature
test safety » tests safety, best safety, rest safety
studien die » studie die, studien der
e literatur » die literatur
studien de » studien der, studien des, studien dd

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 safety ((studien de) OR (studien die)) filosofia ((e literature) OR (e literatur)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "test safety ((studien de) OR (studien die)) filosofia ((e literature) or (e literatur))".
• Adding a wildcard symbol may retrieve word variants: test safety ((studien de) OR (studien die)) filosofia ((e literature) or (e literatur))*.