Alves, C. O., and G. M. Figueiredo. “Existence and Concentration of Nodal Solutions to a Class of Quasilinear Problems”. Topological Methods in Nonlinear Analysis, vol. 29, no. 2, June 2007, pp. 279-93, https://apcz.umk.pl/TMNA/article/view/TMNA.2007.012.