An asymptotic study of a weakly nonlinear multifrequency oscillating system. Neliniini Kolyvannya, [S. l.], v. 13, n. 3, p. 314–327, 2010. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/567. Acesso em: 21 jan. 2026.