Rossi, A. V.; Tubino, M. About the Kinetics and Mechanism of the Reactions of 4-(2-Pyridylazo) Resorcinol, With Zn2+, Cu2+ and Zn2+ +Cu2+ Equimolar Mixtures, in Aqueous Solutions. Eclet. Quim. 2003, 28, 55-62.