Cabré, Xavier, and Luis A. Caffarelli. “Regularity for Viscosity Solutions of Fully Nonlinear Equations $F(D^2u) = 0$”. Topological Methods in Nonlinear Analysis 6, no. 1 (September 1, 1995): 31–48. Accessed October 5, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.1995.030.