Passaseo, D. “Multiplicity of Nodal Solutions for Elliptic Equations With Supercritical Exponent in Contractible Domains”. Topological Methods in Nonlinear Analysis, vol. 8, no. 2, Dec. 1996, pp. 245-62, https://apcz.umk.pl/TMNA/article/view/TMNA.1996.031.