DAO, Nguyen Van. A note on nonlinear systems with different degrees of excitations. <b>Vietnam Journal of Mechanics</b>, Hanoi, Vietnam, v. 16, n. 3, p. 47–49, 1994. DOI: 10.15625/0866-7136/10174. Disponível em: https://vjmech.vast.vn/vjmech/article/view/10174. Acesso em: 9 nov. 2025.