URMANCHEV, V. I. Qualitative Investigation of Discontinuous Dynamical Systems on a Plane by the Method of Pointwise Mappings. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 56, n. 1, p. 108–118, 2004. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3732. Acesso em: 14 apr. 2025.