B, T., and V. M. “Quasiclassical Approach to Tunnel Ionization in the Non Relativistic and Relativistic Regimes”. Revista Mexicana De Física, vol. 60, no. 4 Jul-Aug, Jan. 2014, pp. 290-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/4089.