1. S. A. Hiller, A. V. Eremeev, M. Yu. Lidak, and V. A. Pestunovich, KhGS [Chemistry of Heterocyclic Compounds], 6, 8, 1970.
2. S. A. Hiller, A. V. Eremeev, and M. Yu. Lidak, KhGS [Chemistry of Heterocyclic Compounds], 6, 3, 1970.
3. E. Fischer, Ber. 29, 795, 1895.
4. H. Bieltz, J. Phys. Chem., 30, 527, 1899.
5. A. E. Arbuzov and Yu. P. Kitaev, DAN, 137, 862, 1961.