Bajpai, A.K., and O.P. Sharma. “Persulphate-Co2+-Bisulphite Initiated Aqueous Polymerization of Acrylamide and Retardation by Organic Solvents ”. Asian Journal of Chemistry, vol. 7, no. 3, Mar. 2010, pp. 635-44, https://asianpubs.org/index.php/ajchem/article/view/24373.