SVISTUN, O. P. On the existence of piecewise-continuous separatrix curves for a certain class of pulse systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 5, p. 580–585, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5720. Acesso em: 5 dec. 2025.