Duc, Duong Minh, Tran Vinh Hung, i Nguyen Tien Khai. „Critical Points of Non-$C^{2}$ Functionals”. Topological Methods in Nonlinear Analysis 29, no. 1 (marzec 1, 2007): 35–68. Udostępniono lipiec 4, 2025. https://apcz.umk.pl/TMNA/article/view/TMNA.2007.003.