Margheri, A., and C. Rebelo. “Multiplicity of Solutions of Asymptotically Linear Dirichlet Problems Associated to Second Order Equations in R^{2n+1}”. Topological Methods in Nonlinear Analysis, vol. 46, no. 2, Dec. 2015, pp. 1107-18, https://apcz.umk.pl/TMNA/article/view/TMNA.2015.083.