1. G. A. Sokol'skii, M. A. Belaventsev, and I. L. Knunyants, Izv. Akad. Nauk SSSR, Ser. Khim.,1967, 1524.
2. R. Schultz- Sellack, Ber.,3, 215 (1870); Bull. Soc. Chim. Belges,14, 154 (1870).
3. M. C. Marignac, Arch. Gen.,22, 225 (1853);52, 236 (1875).
4. M. G. Oddo, Gazz. Chim. Ital.,31 II, 158 (1901); Bull. Soc. Chim. France, [3],25, 897 (1901); Chem. Zentr.,1901 II, 969.
5. R. Schenk, Liebigs Ann. Chem.,316, 1 (1901).