UDDIN, M. A.; SATTAR, M. A. Second Approximate Solution of Duffing Equation with Strong Nonlinearity by Homotopy Perturbation Method. GANIT: Journal of Bangladesh Mathematical Society, [S. l.], v. 30, p. 59–75, 2011. DOI: 10.3329/ganit.v30i0.8504. Disponível em: https://banglajol.info/index.php/GANIT/article/view/8504. Acesso em: 24 sep. 2022.