Singh, Lakshman, et al. “Infrared and Thermal Studies of Some Six-Coordinated Zirconium(IV) Complexes of Schiff Bases of 4-Aminoantipyrine‡ ”. Asian Journal of Chemistry, vol. 9, no. 4, Mar. 2010, pp. 831-6, https://asianpubs.org/index.php/ajchem/article/view/23973.