The complex-valued functions
defined on a subset S of the plane such that (S−− S)−∩ S is empty which give
strong-operator continuous mappings from the set of normal operators on a Hilbert
space with spectra in S into the set of all normal operators are characterized as those
which are continuous on S, bounded on bounded subsets of S and O(z)
(Theorem 4.2). In the process of proving this result, it is shown that the
adjoint operation is strong-operator continuous on the set of normal operators
(Theorem 4.1).