Perhaps you should try some spelling variations:
"la retrieval conference" » "la retrieval inference", "la retrieval preference", "la retrieval references", "a retrieval conference", "das retrieval conference", "via retrieval conference"
"la original conference" » "la regional conference", "la regional conferences", "la optical conference", "a original conference", "das original conference", "_ original conference"
"la retinal conference" » "la regional conference", "la regional conferences", "la national conference", "a retinal conference", "day retinal conference", "_ retinal 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 original conference") OR ((("la retinal conference") OR ("la retrieval conference")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"la original conference\") or (((\"la retinal conference\") OR (\"la retrieval conference\"))))".
• Removing quotes may allow a broader search: (( la original conference ) or ((( la retinal conference ) OR ( la retrieval conference )))).
• Adding a wildcard symbol may retrieve word variants: (("la original conference") or ((("la retinal conference") OR ("la retrieval conference"))))*.