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

In the above-titled paper (ibid., vol.36, no.6, p.742-6, June 1991), the authors gave necessary and sufficient conditions for the Schur stability of nonnegative interval matrices. The commenter suggests that these conditions may be more conveniently stated in terms of characteristics of M-matrices and are easy consequences of some well-known facts in nonnegative matrix theory. The M-matrix characterization further reveals that the conditions in the above-titled paper fall into a special case of a known result for the general interval matrices.<>