1. Zollinger, H., Color Chemistry, 2nd ed., VCH, Weinheim, 1991, Chapter 7.7.
2. Schwander, H. R., Dyes Pigm., 3 (1982) 133.
3. Weaver, M. A. and Shuttleworth, L., Dyes Pigm., 3 (1982) 81.
4. Dawson, J. F., J. Soc. Dyers Colour, 99 (1983) 183.
5. Dawson, J. F., Rev. Progr. Coloration 14 (1984) 90.