Jan, M. Q., and M. T. Shah. “Ni, Cr, Cu, Zn, Co, Ag, and Au Content of Some Tal-Carbonate Rocks from NWFP, Pakistan”. Journal of Himalayan Earth Sciences, vol. 20, no. 1, Mar. 1987, pp. 215-6, http://ojs.uop.edu.pk/jhes/article/view/1327.