YEVSTAFYEVA, V. V. Periodic solutions of a system of differential equations with hysteresis nonlinearity in the presence of eigenvalue zero. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 8, p. 1085–1096, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1619. Acesso em: 5 dec. 2025.