1. J. R. Hannay,J. Soc. Dyers Colour.,28, 20 (1912).
2. C. C. Wilcock and C. P. Tattersfield,J. Soc. Dyers Colour.,59, 119 (1943).
3. J. M. Matthews, “Application of Dyestuffs”, pp.53, 166, 281, John Wiley, New York, 1947.
4. A. Schmitz,J. Soc. Dyers Colour.,71, 910 (1955).
5. K. Venkataraman, “The Chemistry of Synthetic Dyes”, Vol. I, Chap. XIV, pp.557, 601, Academic Press, New York, 1952.