Perhaps you should try some spelling variations:
"World Bank regional and sectional studies" » "World Bank regional and functional studies", "World Bank regional and regional studies", "World Bank regional and observational studies"
"world bank regional and sectoral studies" » "world bank regional and spectral studies", "world bank regional and sector studies", "world bank regional and doctoral studies", "world lanka regional and sectoral studies", "world mask regional and sectoral studies", "world park regional and sectoral studies"

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 bank regional and sectoral studies") OR ((("World Bank regional and sectional studies") OR ("World Bank regional and sectional study")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"world bank regional and sectoral studies\") or (((\"World Bank regional and sectional studies\") OR (\"World Bank regional and sectional study\"))))".
• Removing quotes may allow a broader search: (( world bank regional and sectoral studies ) or ((( World Bank regional and sectional studies ) OR ( World Bank regional and sectional study )))).
• Adding a wildcard symbol may retrieve word variants: (("world bank regional and sectoral studies") or ((("World Bank regional and sectional studies") OR ("World Bank regional and sectional study"))))*.