A.H, Z., S. Rohani K, N. Adillah A, S. M, and N. A. “Effect of Ascorbic Acid, Alpha-Tocopherol, Beta-Carotene and Total Polyphenol on Antioxidant Activity in Selected Malaysian Edible Plants”. Malaysian Journal of Science, vol. 24, no. 1, Jan. 2005, pp. 219-24, http://mjs.um.edu.my/index.php/MJS/article/view/8981.