DAO, N. V. Subharmonic oscillation in third order non-linear systems. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 1, n. 3-4, p. 12–20, 1979. DOI: 10.15625/0866-7136/9895. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/9895. Acesso em: 18 apr. 2024.