Benci, V., A. M. Micheletti, and D. Visetti. “An Eigenvalue Problem for a Quasilinear Elliptic Field Equation on $\mathbb R^n$”. Topological Methods in Nonlinear Analysis, vol. 17, no. 2, June 2001, pp. 191-1, https://apcz.umk.pl/TMNA/article/view/TMNA.2001.013.