1. A. T. Balaban, A. Dinculescu, G. N. Dorofeenko, G. W. Fischer, A. V. Koblik, V. V. Mezheritskii, W. Schroth, Pyrylium Salts: Syntheses, Reactions, and Physical Properties, Academic Press, 1982, p. 77.
2. G. N. Dorofeenko, E. I. Sadekova, E. V. Kuznetsov, Preparativnaya khimiya pirilievykh solei [The Preparative Chemistry of Pyrylium Salts], Izd. Rostov. Univ., 1972, 234 pp. (in Russian).
3. D. Eastwood, C. Fernandes, B. Yunghoon Yoon, C. N. Sheaff, Ch. M. Wai, Appl. Spectrosc., 2006, 60, 958.
4. B. Caro, F. Le Guen-Robin, M. Salmain, G. Jaouen, Tetrahedron, 2000, 56, 257.
5. K. Höfelschweiger, The Pyrylium Dyes: A New Class of Biolabels. Synthesis, Spectroscopy, and Application as Labels and in General Protein Assay, Regensburg, 2005.