KOSHLYAKOV, V. N. Method of averaging in the problem of stability of motion of a body suspended from a string. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 4, p. 467–475, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3321. Acesso em: 11 apr. 2025.