Rai, Rajeshwar, et al. “Synthesis and Spectroscopic Investigations of Schiff Bases Transition Metal Complexes of Copper(II), Cobalt(II) and Nickel(II)”. Asian Journal of Chemistry, vol. 29, no. 12, Oct. 2017, pp. 2707-10, doi:10.14233/ajchem.2017.20819.