Willard, H. H; Manalo, G. D (1947). "Derivatives of Diphenylamine as Oxidation-Reduction Indicators in Alkaline Solution". Analytical Chemistry. 19 (3): 167–170. doi:10.1021/ac60003a011.
dx.doi.org
P. F. Vogt, J. J. Gerulis, "Amines, Aromatic" in Ullmann’s Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a02_037