PETRYSHYN, R. I.; Sopronyuk Т. M. Justification of Averaging Method for Multifrequency Impulsive Systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 1, p. 55–65, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3887. Acesso em: 6 dec. 2025.