Diaz, R., D. Gonzalez, F. Marin, and R. Martinez. “Comparative Kinetics of the Snowball Respect to Other Dynamical Objects”. Revista Mexicana De Física E, vol. 50, no. 1 Jan-Jun, Jan. 2004, pp. 65-73, https://rmf.smf.mx/ojs/index.php/rmf-e/article/view/4465.