Jinnapat , A., and A. Rattanasing. “A study of absorption capacity of zinc ions onto coffee residue activated carbon”. NKRAFA JOURNAL OF SCIENCE AND TECHNOLOGY, vol. 17, no. 2, Dec. 2021, pp. 69-78, https://ph02.tci-thaijo.org/index.php/nkrafa-sct/article/view/245521.