Sierra-Porta, D., M. Chirinos, and J. Stock. “Comparison of Solutions to the Thomas-Fermi Equation by a Direct Method and Variational Calculus”. Revista Mexicana De Física, vol. 63, no. 4 Jul-Aug, Jan. 2017, pp. 333-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/351.