DAO, N. V. A note on nonlinear systems with different degrees of excitations. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 16, n. 3, p. 47–49, 1994. DOI: 10.15625/0866-7136/10174. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/10174. Acesso em: 20 apr. 2024.