It is shown, that Theorem 1.2 of Willems (Operators, Systems and Linear Alg
ebra (Kaiserslautern, 1997), European Consort. Math. Indust., Jeubner, Stug
gart, 1997, pp. 214-223), is analog of the outcomes of the statement 5 (Ali
ev and Lorin, Systems Contr. Lett. 21 (1993) 485-491). (C) 1999 Elsevier Sc
ience B.V. All rights reserved.