DUDZYANYI, S. I.; PERESTYUK, N. A. On the stability of an invariant torus. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 9, p. 1212–1222, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5120. Acesso em: 5 dec. 2025.