1. Leonid M. Kogan, V. E. Gulaya, and I. V. Torgov, Tetrahedron Lett., 4763 (1967).
2. S. N. Ananchenko and I. V. Torgov, Dokl. Akad. Nauk SSSR,127, 553 (1959).
3. C. Tamm, Helv. Chim. Acta,38, 338 (1960).
4. N. Bkhakka and D. Williams, Application of NMR in Organic Chemistry [Russian translation], Mir (1966), p. 109.
5. V. L. Sadovskaya, N. S. Vul'fson, and V. I. Zaretskii, Izv. Akad. Nauk SSSR, Ser. Khim., 2767 (1967).