Perhaps you should try some spelling variations:
"la regional conferences" » "la regional conference", "la regional consequences", "la regional differences", "a regional conferences", "ia regional conferences", "sea regional conferences"
"das original conference" » "das regional conference", "das retinal conference", "das final conference", "his original conference", "its original conference"
"das optical conference" » "das optical coherence", "das topical conference", "das practical conference", "cas optical conference", "das optimal conference", "gas optical conference"

Try widening your search to All Fields.

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: (("la regional conferences") OR ((("das original conference") OR ("das optical conference")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"la regional conferences\") or (((\"das original conference\") OR (\"das optical conference\"))))".
• Removing quotes may allow a broader search: (( la regional conferences ) or ((( das original conference ) OR ( das optical conference )))).
• Adding a wildcard symbol may retrieve word variants: (("la regional conferences") or ((("das original conference") OR ("das optical conference"))))*.