Ovsiyuk, E. M., and O. V. Veko. “On Behavior of Quantum Particles in an Electric Field in Spaces of Constant Curvature, Hyperbolic and Spherical Models”. Ukrainian Journal of Physics 58, no. 11 (October 11, 2018): 1065. Accessed November 27, 2020. https://ujp.bitp.kiev.ua/index.php/ujp/article/view/2018386.