WEBB, J. R. L. A class of positive linear operators and applications to nonlinear boundary value problems. Topological Methods in Nonlinear Analysis, [S. l.], v. 39, n. 2, p. 221–242, 2012. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2012.013. Acesso em: 19 apr. 2024.