Masae, Mahamasuhaimi, Lek Sikong, Peerawas Kongsong, Phatcharee Phoempoon, Surasit Rawangwong, and Witthaya Sririkun. 2016. “Application of Rubber Wood Ash for Removal Nickel and Copper from Aqueous Solution”. Environment and Natural Resources Journal 11 (2). Nakhon Pathom, Thailand:17-27. https://ph02.tci-thaijo.org/index.php/ennrj/article/view/71253.