Before revision: See also Polilov's theorem References V. L. Kharitonov, "Asymptotic stability of an equilibrium position of a family of systems of differential equations", Differentsialnye uravneniya'', 14 (1978), 2086-2088.
After revision: References V. L. Kharitonov, "Asymptotic stability of an equilibrium position of a family of systems of differential equations", Differentsialnye uravneniya'', 14 (1978), 2086-2088.