Mallick, Mohan, and Ram Baran Verma. “A Three Solutions Theorem for Pucci’s Extremal Operator and Its Application”. Topological Methods in Nonlinear Analysis 58, no. 1 (September 12, 2021): 161–179. Accessed April 25, 2024. https://apcz.umk.pl/TMNA/article/view/35210.