URMANCHEV, V. I. A stability criterion for periodic solutions of two-dimensional discontinuous dynamical systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 9, p. 1262–1266, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4721. Acesso em: 5 dec. 2025.