Rahman, S., S. Waheed, and N. Siddique. “CLASSIFICATION OF CALCIUM SUPPLEMENTS THROUGH APPLICATION OF PRINCIPAL COMPONENT ANALYSIS: A STUDY BY INAA AND AAS”. The Nucleus, vol. 50, no. 2, May 2013, pp. 117-24, http://thenucleuspak.org.pk/index.php/Nucleus/article/view/761.