Perhaps you should try some spelling variations:
heilkunde 15.15 » heilkunde 5.1, heilkunde 11
heilkunde 1991 » heilkunde 11, heilkunde 1, heilkunde 10
verh.bern.dt.geld.hno- » very.bern.dt.geld.hno-, ver.bern.dt.geld.hno-, verb.bern.dt.geld.hno-, verh.been.dt.geld.hno-, verh.born.dt.geld.hno-, verh.bern.dt.gold.hno-, verh.bern.dt.gel.hno-
vers.bern.dt.gels.hno- » vers.been.dt.gels.hno-, vers.born.dt.gels.hno-, verse.bern.dt.gels.hno-, verso.bern.dt.gels.hno-, very.bern.dt.gels.hno-, vers.bern.dt.gel.hno-, vers.bern.dt.gets.hno-
vers.ben.dt.gels.hno- » verse.ben.dt.gels.hno-, verso.ben.dt.gels.hno-, very.ben.dt.gels.hno-, vers.ben.dt.gel.hno-, vers.ben.dt.gets.hno-, vers.been.dt.gels.hno-

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: (( verh.bern.dt.geld.hno-((heilkunde 1991) OR (heilkunde 15.15)) ) OR ( (vers.bern.dt.gels.hno- OR vers.ben.dt.gels.hno-)((heilkunde 1991) OR (heilkunde 15.15)) )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( verh.bern.dt.geld.hno-((heilkunde 1991) or (heilkunde 15.15)) ) or ( (vers.bern.dt.gels.hno- OR vers.ben.dt.gels.hno-)((heilkunde 1991) or (heilkunde 15.15)) ))".
• Adding a wildcard symbol may retrieve word variants: (( verh.bern.dt.geld.hno-((heilkunde 1991) or (heilkunde 15.15)) ) or ( (vers.bern.dt.gels.hno- OR vers.ben.dt.gels.hno-)((heilkunde 1991) or (heilkunde 15.15)) ))*.