DINH, N. V. A modified asymptotic method for a Van-der-Pol oscillator with large cubic restoring nonlinearity. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 26, n. 2, p. 122–128, 2004. DOI: 10.15625/0866-7136/26/2/5696. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/5696. Acesso em: 2 jul. 2022.