CHABROWSKI, Jan; WILLEM, Michael. On multiple solutions of the exterior Neumann problem involving critical Sobolev exponent. Topological Methods in Nonlinear Analysis, [S. l.], v. 26, n. 1, p. 89–108, 2005. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2005.026. Acesso em: 26 jun. 2026.