Sunoj B S , Mathew Varkey T K. “Oblong Difference Mean Prime Labeling of Some Planar Graphs”. International Journal of Emerging Trends in Science and Technology, Vol. 4, no. 11, Nov. 2017, pp. 6344-8, https://igmpublication.org/ijetst.in/index.php/ijetst/article/view/1196.