Sapaw, R., brahim Ahmad, A. Zaharim, A. Dolah, S. K. Sahar, and N. Rajaee. “E-Beam Metallization and Optimization Using Second-Order Single Response Surface Methodology”. Malaysian Journal of Science, vol. 24, no. 2, Aug. 2005, pp. 97-108, https://malindojournal.um.edu.my/index.php/MJS/article/view/8349.