Arifien, A.E. “Spectrophotometric Study of the Complexation Equilibria of Vanadium(V) With 3,5-Diaminoaza-Pyrazole Derivatives ”. Asian Journal of Chemistry, vol. 4, no. 4, Mar. 2010, pp. 804-11, https://asianpubs.org/index.php/ajchem/article/view/25155.