Kshirsagar, Versha, et al. “Amperometric Determination of Nickel(II), Copper(II), Zinc(II) and Cadmium(II) Using 3-Phenyl Rhodanine”. Asian Journal of Chemistry, vol. 18, no. 4, Mar. 2010, pp. 3233-5, https://asianpubs.org/index.php/ajchem/article/view/20822.