Perera, K., Agarwal, R. P. and O’Regan, D. (2010) “Nontrivial solutions of $p$-superlinear anisotropic $p$-Laplacian systems via Morse theory”, Topological Methods in Nonlinear Analysis, 35(2), pp. 367–378. Available at: https://apcz.umk.pl/TMNA/article/view/TMNA.2010.021 (Accessed: 3 July 2024).