1. E. V. Titov, L. M. Litvinenko, N. F. Levchenko, and N. A. Izmailov, Ukr. khim. zhurnal, 27, 481, 1961.
2. E. V. Titov, L. M. Litvinenko, and N. A. Izmailov, Ukr. khim. zhurnal, 27, 87, 1961.
3. E. V. Titov, M. V. Poddubnaya, and L. M. Litvinenko, TEKh [Theoretical and Experimental Chemistry], 2, 271, 1966.
4. D. Prevor?ek, Bull. Soc. Chim. France, 795, 1958.
5. M. Mashima, Bull. Soc. Chem. Japan, 35, 11, 1882, 1962; 35, 2, 332, 1960.