1. P. V. Klevtsov, R. F. Klevtsova, and L. P. Sheina, Zh. Strukt. Khimii,6, 469 (1965).
2. R. F. Klevtsova and P. V. Klevtsov, Dokl. AN SSSR,162, 1049 (1965).
3. R. F. Klevtsova and P. V. Klevtsov, Zh. Strukt. Khimii,5, 860 (1964).
4. F. A. Brusentsev, S. V. Borisov, and R. F. Klevtsova, Zh. Strukt. Khimii,6, 567 (1965).
5. W. Feitknecht, Helv. Chim. Acta.,19, 467 (1936).