Philip, J. Y. N. ., S. . John, and O. C. . Othman. “Levels of Heavy Metals in Selected Facial Cosmetics Marketed in Dar Es Salaam, Tanzania”. Tanzania Journal of Science, vol. 44, no. 2, July 2018, pp. 81-88, http://www.tjs.udsm.ac.tz/index.php/tjs/article/view/246.