Din, F., and M. Rafiq. “Correlation Between Compressive Strength and Tensile Strength/ Index Strength of Some Rocks of North-West Frontier Province (Limestone and Granite)”. Journal of Himalayan Earth Sciences, vol. 30, no. 1, Mar. 1997, pp. 183-90, http://ojs.uop.edu.pk/jhes/article/view/1504.