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2. Ya. Z. Tsypkin, Relay Systems [in Russian], Nauka, Moscow (1974).
3. Yu. I. Neimark, Point Mapping Method in Nonlinear System Theory [in Russian], Nauka, Moscow (1972).
4. É. V. Gaushus, Analysis of Dynamic Systems by Point Mapping Method [in Russian], Nauka, Moscow (1976).
5. N. S. Postnikov, “Stochastic oscillations in a relay system with hysteresis,” 6th All-Union Conf. on Control in Mechanical Systems, abstracts of papers [in Russian], L'vov Univ. (1988), p. 129.