Comments on 'Limit cycles due to roundoff in state-space digital filters' [and reply]

Theorem 1 of the above-named correspondence by T. Bose and D.P. Brown (IEEE Trans. Acoust. Speech Signal Process. vol.38, no.8, pp.1460-2, Aug. 1990) is shown to be generally incorrect. As a consequence, the conclusion does not apply. T. Bose and D.P. Brown clarify their intent and make a change to the statement of the theorem, restricting it to induced q-norms rather than induced norms in general. >