M. A. Amatov, “Periodic solutions of a nonlinear system”, Differ. Uravn., 17:11 (1981), 2084–2085
1977
2.
M. A. Amatov, “A criterion for the uniqueness of periodic solutions”, Izv. Vyssh. Uchebn. Zaved. Mat., 1977, no. 9, 3–5; Soviet Math. (Iz. VUZ), 21:9 (1977), 1–2
1973
3.
M. A. Amatov, “Periodic solutions of a certain autonomous system of ordinary differential equations with discontinuous right-hand sides”, Differ. Uravn., 9:11 (1973), 1937–1944