Lilly, K.O., et al. “Tetradentate Schiff Base Chelates of Copper(II) and Nickel(II):Halogenation and Phenylisocyanation”. Asian Journal of Chemistry, vol. 16, no. 1, July 2012, pp. 331-7, https://asianpubs.org/index.php/ajchem/article/view/19620.