1. A. E. Chichibabin, Fundamental Principles of Organic Chemistry (Gos. Izd. Khim. Liter., Moscow, 1957), Vol. 2 [in Russian].
2. www.answers.com/topic/azobenzene
3. I. M. Kogan, Chemistry of Dyes (Syntetic) (Glav. Redaktsiya Khim. Liter., Moscow, 1938), p. 72 [in Russian].
4. P. F. Gordon and P. Gregory, Organic Chemistry in Colour (Springer, Berlin, 1983).
5. A. N. Terenin, Photonics of Molecules of Dyes and Related Organic Compounds (Nauka, Leningrad, 1967) [in Russian].