1. B. M. Krasovitskii and B. M. Bolotin, Organic Luminophores [in Russian], Khimiya, Moscow (1984).
2. J. Cornforth, in: Heterocyclic Compounds, R. Elderfield (ed.) [Russian translation], Vol. 5, IL, Moscow (1961).
3. W. Theilacker, J. Prakt. Chem.,153, 54 (1939).
4. M. I. Shenbor and V. N. Tikhonov, Khim. Geterotsikl. Soedin., No. 5, 608 (1973).
5. B. Eistert, W. Eifler, and H. Goth, Chem. Ber.,101, 2162 (1968).