Saccon, Claudio. “Multiplicity of Bifurcation Points for Variational Inequalities via Conley Index”. Topological Methods in Nonlinear Analysis 11, no. 1 (March 1, 1998): 83–102. Accessed April 19, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.1998.005.