Duarte, Ronaldo C., and Marco A. S. Souto. “Nonlocal Schrödinger Equations for Integro-Differential Operators With Measurable Kernels”. Topological Methods in Nonlinear Analysis, vol. 54, no. 1, July 2019, pp. 383-06, https://apcz.umk.pl/TMNA/article/view/TMNA.2019.056.