Dakshene, Monika, and Renuka Jain. “Removal of Tannic Acid from Aqueous Waste Over NaOH Treated Power Plant Fly-Ash”. Asian Journal of Chemistry, vol. 23, no. 4, Dec. 2010, pp. 1706-8, https://asianpubs.org/index.php/ajchem/article/view/10170.