Sultana, M., and M. Khalid. “FORMATION OF LOPSIDED AND BAR STRUCTURES IN NON-STATIONARY GRAVITATING SYSTEMS. I- ISOTROPIC CASE”. The Nucleus, vol. 50, no. 3, Sept. 2013, pp. 285-8, http://thenucleuspak.org.pk/index.php/Nucleus/article/view/757.