FENG, X.; HE, Y.; MENG, J. Application of homotopy perturbation method to the Bratu-type equations. Topological Methods in Nonlinear Analysis, [S. l.], v. 31, n. 2, p. 243–252, 2008. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2008.015. Acesso em: 16 oct. 2021.