CLAPP, M.; IZQUIERDO, G. Multiple positive symmetric solutions of a singularly perturbed elliptic equation. Topological Methods in Nonlinear Analysis, [S. l.], v. 18, n. 1, p. 17–39, 2001. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2001.022. Acesso em: 25 apr. 2024.