DAO, Nguyen Van. Some problems on nonlinear oscillations. <b>Vietnam Journal of Mechanics</b>, Hanoi, Vietnam, v. 29, n. 3, p. 187–195, 2007. DOI: 10.15625/0866-7136/29/3/5531. Disponível em: https://vjmech.vast.vn/vjmech/article/view/5531. Acesso em: 9 nov. 2025.