  This paper is concerned with the notions of admissibility, exact
controllability, exact observability and regularity of linear systems in the
Banach space setting. It is proved that admissible controllability, exact
controllability, admissible observation, exact observability and regularity are
invariant under some regular perturbations of the generators, such results are
generalizations of some previous references. Moreover, the related boundary
linear systems and some illustrative examples are presented.
