1. (a) Recent reviews of polymethine dyes: Stroenie i Tsvet Polimetinovykh Krashelei (Structure and Color of Polymethine Dyes). Naukova Dumka, Kiev (1989).
2. (b) ?Methine Dyes and Pigments?, in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., Vol. A16, pp. 487-534. VCH, Weinheim (1990).
3. (c) Color Chemistry, 2nd ed. VCH, Weinheim (1991).
4. (d) and Polymethine Dyes?Structure and Properties. St. Kliment Ohridski University Press, Sofia (1991).