Comments on "A necessary and sufficient condition for the stability of nonnegative interval discrete systems" by B. Shafai et al

It is shown that a necessary and sufficient condition for the stability of nonnegative interval discrete systems reported in the above-named work (ibid., vol.36, no.6, p.742-6, June 1991) can be alternatively be established by using a previous work of the present authors (Memoirs, Fac. Eng., Kyoto Univ. vol.49, no.4, p.273-9, 1987) and properties of M-matrices, and furthermore it ensures the stability of an even wider class of systems.<
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