DINH, N. V.; TRI, T. D. The Poincaré method for an oscillator with quadratic nonlinearity. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 26, n. 1, p. 23–30, 2004. DOI: 10.15625/0866-7136/26/1/5686. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/5686. Acesso em: 20 jun. 2024.