Comments on "Stabilizability and detectability of discrete-time time-varying systems" by J.C. Engwerda [with reply]

In the original paper (ibid., vol.35, p.425-9, Apr. 1990), Engwerda analysed discrete-time and time-varying systems by resorting to systems that have time-varying order. Some comments are made on this issue. Moreover, Engwerda presented a counterexample which was claimed to contradict a result of B.D.O. Anderson and J.B. Moore (1981). The commenters show that such a counterexample does not actually entail any contradiction. In reply, Engwerda shows that there is an error in the work of Anderson and Moore that explains why his counterexample does not work.<
>