Masoud, Mamdouh Saad, et al. “Solvatochromism and Potentiometic Studies of Some Active Nitroso- and Nitroso-Azo- Compounds”. European Journal of Chemistry, vol. 2, no. 3, Sept. 2011, pp. 420-32, doi:10.5155/eurjchem.2.3.420-432.407.