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

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 ((studien la) OR (studien lap)) filosofia del literature*".