Letter to the Editor—Acknowledgment

Professor Richard Serfozo has pointed out to us that our theorem (Derman, C., E. Ignall. 1975. On the stochastic ordering of Markov chains. Opns. Res.23 574–576.) is not new, being essentially equivalent to theorem 2 of Kalmykov, G. I. 1962. On the partial ordering of one-dimensional Markov processes. Theor. Probab. Appl.7 456–459.