SAMOILENKO, A. M.; SAMOILENKO, V. G.; SOBCHUK, V. S. On periodic solutions of the equation of a nonlinear oscillator with pulse influence. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 6, p. 827–834, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4669. Acesso em: 11 apr. 2025.