“…Most studies about the neutral initial value problems governed by retarded semilinear parabolic equation have been devoted to the control problems. As for the retarded differential equations, Jeong et al [12,13], Sukavanam et al [22], and Wang [25], have discussed the regularity of solutions and controllability of the semilinear retarded systems, and see [12,13,22,25] and references therein for the linear retarded systems.…”