Perhaps you should try some spelling variations:
"a original conference" » "a regional conference", "a regional conferences", "a optical conference", "_ original conference", "2 original conference", "1 original conference"
"la retinal conference" » "la regional conference", "la regional conferences", "la retrieval conference", "a retinal conference", "cat retinal conference", "5 retinal conference"
"_ retinal conference" » "_ regional conference", "_ regional conferences", "_ retrieval 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 retinal conference") OR ("_ retinal conference"))) OR ("a original conference")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"la retinal conference\") OR (\"_ retinal conference\"))) or (\"a original conference\"))".
• Removing quotes may allow a broader search: (((( la retinal conference ) OR ( _ retinal conference ))) or ( a original conference )).
• Adding a wildcard symbol may retrieve word variants: (((("la retinal conference") OR ("_ retinal conference"))) or ("a original conference"))*.