HABETS, Patrick; GAUDENZI, Marcellino. Existence and multiplicity of positive solutions for boundary value problems of 2d order ODE. Topological Methods in Nonlinear Analysis, [S. l.], v. 14, n. 1, p. 131–150, 1999. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1999.024. Acesso em: 8 jul. 2025.