Njue, W. W., R. Wanjau, and N. I. Kariuki. “Analysis of Essential Trace Elements by EDXRF in Selected Medicinal Plants Used in Kenya”. The International Journal of Science & Technoledge, vol. 4, no. 1, Jan. 2016, http://internationaljournalcorner.com/index.php/theijst/article/view/123729.