Perhaps you should try some spelling variations:
passiver » passiven, passively, passiert
passiverer » passivener, passivelyer, passierter, passiverwerb, passivieren, passieren
passivelyen » passively
passierter » passierte, passiert, passieren

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: ((passiver OR (passive OR passivelyen)) OR (passiverer OR passierter)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((passiver or (passive or passivelyen)) or (passiverer OR passierter))".
• Adding a wildcard symbol may retrieve word variants: ((passiver or (passive or passivelyen)) or (passiverer OR passierter))*.