1. V. D. Orlov, M. A. Aziz, A. T. Savran, and P. K. D. Asoka, Khim. Geterotsikl. Soedin., No. 7, 965 (1984).
2. F. Carey and R. Sundberg, Advanced Organic Chemistry, Part A, Plenum Press (1977).
3. G. F. Duffin and T. D. Kendall, J. Chem. Soc., No. 1, 408 (1954).
4. J. Zollinger, Diazo and Azo Chemistry, Wiley (1961).
5. B. A. Porai-Koshits, Azo Dyes [in Russian], Khimiya, Leningrad (1972), pp. 48, 50, 59.