Ivochkina, Nina, and Nadezhda V. Filimonenkova. “On Two Symmetries in the Theory of $m$-Hessian Operators”. Topological Methods in Nonlinear Analysis 52, no. 1 (February 12, 2018): 31–47. Accessed April 25, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2017.035.