In the technical note by Su (1995) the asymptotic stability of linear systems with commensurate time delays is studied. Algorithms are given for two purposes, namely to check if a given system is asymptotically stable independent of delay, and to determine the largest delay time the system can tolerate to preserve its asymptotic stability. In this note we present new and simpler expressions of the main results presented by Su (1995) with a much simpler proof.
Luo, J. S., & Bosch, van den, P. P. J. (1997). Correspondence A note on 'The asymptotic stability of linear autonomous systems with commensurate time delays'. International Journal of Control, 68(4), 943-946. https://doi.org/10.1080/002071797223424