Prakash, D., et al. “Structural Aspects of Mixed Ligand Complexes of Ni(II) or Cu(II) Metal Chelates of Organic Acids With Ethylenediamine”. Asian Journal of Chemistry, vol. 23, no. 1, Sept. 2010, pp. 281-4, https://asianpubs.org/index.php/ajchem/article/view/10128.