Yang, M., and Y. Ding. “Stationary States for Nonlinear Dirac Equations With Superlinear Nonlinearities”. Topological Methods in Nonlinear Analysis, vol. 39, no. 1, Apr. 2012, pp. 175-88, https://apcz.umk.pl/TMNA/article/view/TMNA.2012.010.