Perhaps you should try some spelling variations:
fuel literature » abel literature, level literature, model literature
filosofia fuel » filosofia del, filosofia de, filosofia e
tests safety » test safety, guests safety, stents safety
studies die » studien die, studies does, studies dose
studie die » studie der

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: "tests safety ((studies die) OR (studie die)) filosofia fuel literature*".