“…A generalization of strongly continuous semigroups, regularized semigroups (Definition 2.1) was introduced, independently, by DA PRATO [4] and DAVIES and PANG [6], and extended in [7]; see also [22], [23], [27], [8] and [9]. Wide classes of operators, A, for which (1.1) may be dealt with using regularized semigroups, but not strongly continuous semigroups, appear in [7], [8], [9] and [10].…”