SAMOILENKO, A. M. Asymptotic method for the investigation of m-frequency oscillation systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 10, p. 1366–1387, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4823. Acesso em: 6 dec. 2025.