Perhaps you should try some spelling variations:
del literature » model literature, abel literature, fuel literature
stents safety » events safety, tenth safety, tests safety
agents safety » patients safety, plants safety, accidents safety
studien la » studien lap, studien a, studien l

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: "((stents safety) OR (agents safety)) studien la filosofia del literature*".