Sharma, R.C., and V.K. Khar. “Synthesis, Characterization and Antimicrobial Studies of Some Macrocyclic Ligands and Their Nickel(II) Complexes ”. Asian Journal of Chemistry, vol. 10, no. 3, Mar. 2010, pp. 467-71, https://asianpubs.org/index.php/ajchem/article/view/23659.