Perhaps you should try some spelling variations:
"world bank regional and electrical services" » "world bank regional and electrical devices", "world bank regional and electrical nerve", "world bank regional and electronic services", "world lanka regional and electrical services", "world mask regional and electrical services", "world urbano regional and electrical services"
"world bank regional and electoral studies" » "world bank regional and sectoral studies", "world bank regional and electrical studies", "world bank regional and doctoral studies", "world lanka regional and electoral studies", "world mask regional and electoral studies", "world urbano regional and electoral studies"
"world park regional and spectral studies" » "world park regional and structural studies", "world park regional and sectional studies", "world park regional and general studies", "world parks regional and spectral studies", "world part regional and spectral studies", "world park region and spectral studies", "world par regional and spectral studies", "world pork regional and spectral studies"

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• If you are trying to use Boolean operators, they must be ALL CAPS: (((("world bank regional and electoral studies") OR ("world park regional and spectral studies"))) OR ("world bank regional and electrical services")).
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• Adding a wildcard symbol may retrieve word variants: (((("world bank regional and electoral studies") or ("world park regional and spectral studies"))) or ("world bank regional and electrical services"))*.