Multivalued nonexpansive mappings and Opial’s condition
E. Lami Dozo · Proceedings of the American Mathematical Society · 1973
We give relations between a condition introduced by Z. Opial which characterizes weak limits by means of the norm in some Banach spaces and approximations of the identity, in particular for systems of projections. Finally a fixed point theorem for multivalued nonexpansive mappings in a Banach space satisfying this condition is proved; this result generalizes those of J. Markin and F. Browder.