CORVELLEC, J.-N.; DEGIOVANNI, M.; MARZOCCHI, M. Deformation properties for continuous functionals and critical point theory. Topological Methods in Nonlinear Analysis, [S. l.], v. 1, n. 1, p. 151–171, 1993. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1993.012. Acesso em: 27 apr. 2024.