State space models using simplified Routh approximation method

For original paper see ibid., vol.23, no.24, p.300 (1987). Sastry et al. proposed a new procedure to obtain the triple of all lower order models in companion form directly, using SRAM. However, some of the claims made by the authors are incorrect and also the method is unduly restricted in its applicability. In particular the authors claim that SRAM retains the first k time moments and also Markov parameters (an implicit assumption) of the full order system in a reduced kth order system. Another implicit claim is that SRAM always results in stable reduced models if the original system is stable. However these claims in general are incorrect.