1. P. Holy, M. Belogradsky, J. Stibor, J. Kondelka, D. Saman, J. Hodacova, A. Holy, and J. Zavada, Coll. Czech. Chem. Commun., 52, No. 12, 2971 (1987).
2. É. I. Ivanova, G. V. Fedorova, O. G. Yasinskaya, A. N. Musienko, V. V. Ivanova, A. V. Mazepa, and B. V. Kunshenko, Khim.-Farm. Zh. No. 9, 66 (1992).
3. R. Elderfield (ed.), Heterocyclic Compounds [Russian translation], Vol. 8, Mir, Moscow (1969), p. 193.
4. R. P. Panzica and L. B. Townsend, J. Heterocycl. Chem., 9, No. 3, 623 (1972).
5. D. Barton and W. Ollis (eds.), General Organic Chemistry [Russian translation], Vol. 1, Khimiya, Moscow (1981), p. 382.