Dehnen, H., and M. Corona-Galindo. “Equation of Motion for Describing a Massive Pulsating System With Spherical Symmetry”. Revista Mexicana De Física E, vol. 61, no. 2 Jul-Dec, Jan. 2015, pp. 81-85, https://rmf.smf.mx/ojs/index.php/rmf-e/article/view/4737.