Yusoff M.S, M., H. Maarop, M. Noorul Ehsan, and H. Harun. “Development of a Nondestructive Quantitative Procedure for the Analysis of Gold in Jewellery”. Malaysian Journal of Science, vol. 21, Dec. 2002, pp. 27-30, https://juku.um.edu.my/index.php/MJS/article/view/8853.