1. M. M. Khapaev, “Singular differential equations in problems of investigation of functions for a constrained extremum,” Dokl. Akad. Nauk SSSR,233, No. 2, 250–252 (1992).
2. Yu. G. Evtushenko and V. G. Zhadan, “Barrier-projection method for nonlinear programming problems,” Zh. Vychisl. Mat. Mat. Fiz.,34, No. 5, 669–683 (1994).
3. S. V. Emel'yanov (ed.), Theory of Variable-Structure Systems [in Russian], Nauka, Moscow (1970).