Holubová, Gabriela, and Petr Nečesal. “Fučík Spectrum in General: Principal Eigenvalues and Inadmissible Sets”. Topological Methods in Nonlinear Analysis 44, no. 1 (April 12, 2016): 11–21. Accessed April 25, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2014.033.