Javadi, H. ., F. . Forouzbakhsh, and A. . Jahanshir. “Definition of Singularity Due to Newton’s Second Law Counteracting Gravity”. Scientific Journal of Pure and Applied Sciences, vol. 2, no. 3, Mar. 2013, pp. 116-24, http://sjournals.com/index.php/sjpas/article/view/989.