HALBOOS, et.al, M. H. N. “Adsorption of Nickel Ions From Aqueous Solutions by Green Tea Waste”. Al-Qadisiyah Journal of Pure Science, Vol. 17, no. 4, Aug. 2017, pp. 59-70, https://journalsc.qu.edu.iq/index.php/JOPS/article/view/482.