Perhaps you should try some spelling variations:
"world apis technical paper" » "world api technical paper", "world apps technical paper", "world basics technical paper", "world kpis technical paper", "world april technical paper"
"world anis technical paper" » "world acids technical paper", "world banks technical paper", "world bands technical paper", "world angus technical paper", "world ai technical paper", "world ages technical paper"
"world anis technical papers" » "world acids technical papers", "world banks technical papers", "world bands technical papers", "world angus technical papers", "world ai technical papers", "world ages technical papers"
"world anti technical papers" » "world api technical papers", "world ai technical papers", "world asi technical papers"

Try widening your search to All Fields.

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• If you are trying to use Boolean operators, they must be ALL CAPS: (("world apis technical paper") OR ((("world anis technical paper") OR ((("world anis technical papers") OR ("world anti technical papers")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"world apis technical paper\") or (((\"world anis technical paper\") or (((\"world anis technical papers\") OR (\"world anti technical papers\"))))))".
• Removing quotes may allow a broader search: (( world apis technical paper ) or ((( world anis technical paper ) or ((( world anis technical papers ) OR ( world anti technical papers )))))).
• Adding a wildcard symbol may retrieve word variants: (("world apis technical paper") or ((("world anis technical paper") or ((("world anis technical papers") OR ("world anti technical papers"))))))*.