IL’YASOV, Yavdat; RUNST, Thomas. On positive solutions of indefinite inhomogeneous Neumann boundary value problems. Topological Methods in Nonlinear Analysis, [S. l.], v. 24, n. 1, p. 41–67, 2004. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2004.019. Acesso em: 8 jul. 2025.