GORBACHUK, T. V.; PERESTYUK, N. A. On the existence of discontinuous limit cycles for one system of differential equations with pulse influence. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 8, p. 1127–1134, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5105. Acesso em: 5 dec. 2025.