AGARWAL, Ravi P.; FILIPPAKIS, Michael E.; O‘REGAN, Donal; PAPAGEORGIOU, Nikolaos S. Multiple Solutions for Doubly Resonant Elliptic Problems Using Critical Groups. CUBO, A Mathematical Journal, [S. l.], v. 10, n. 3, p. 21–41, 2008. Disponível em: https://cubo.ufro.cl/index.php/cubo/article/view/1497. Acesso em: 3 nov. 2025.