Perhaps you should try some spelling variations:
heilkunde 1991 » heilkunde 11, heilkunde 15.15, heilkunde 10
heilkunde 1 » heilkunde 10, heilkunde 11, heilkunde 16
vers.bern.dt.gel.hno- » verse.bern.dt.gel.hno-, verso.bern.dt.gel.hno-, ver.bern.dt.gel.hno-, vers.been.dt.gel.hno-, vers.ben.dt.gel.hno-
verh.born.dt.gels.hno-heilkunde » ver.born.dt.gels.hno-heilkunde, verb.born.dt.gels.hno-heilkunde, verm.born.dt.gels.hno-heilkunde, verh.born.dt.geld.hno-heilkunde
vera.born.dt.gels.hno-heilkunde » vera.born.dt.geld.hno-heilkunde, ver.born.dt.gels.hno-heilkunde, verb.born.dt.gels.hno-heilkunde
very.born.dt.gets.hno-heilkunde » very.born.dt.get.hno-heilkunde

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: (( vers.bern.dt.gel.hno-((heilkunde 1991) OR (heilkunde 1)) ) OR (( (verh.born.dt.gels.hno-heilkunde OR vera.born.dt.gels.hno-heilkunde) OR very.born.dt.gets.hno-heilkunde) 1991 )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( vers.bern.dt.gel.hno-((heilkunde 1991) or (heilkunde 1)) ) or (( (verh.born.dt.gels.hno-heilkunde OR vera.born.dt.gels.hno-heilkunde) or very.born.dt.gets.hno-heilkunde) 1991 ))".
• Adding a wildcard symbol may retrieve word variants: (( vers.bern.dt.gel.hno-((heilkunde 1991) or (heilkunde 1)) ) or (( (verh.born.dt.gels.hno-heilkunde OR vera.born.dt.gels.hno-heilkunde) or very.born.dt.gets.hno-heilkunde) 1991 ))*.