SFECCI, Andrea. Double resonance in Sturm-Liouville planar boundary value problems. Topological Methods in Nonlinear Analysis, [S. l.], v. 55, n. 2, p. 655–679, 2020. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2019.109. Acesso em: 8 jul. 2025.