1. Bertrand: Compt. rend. 139, 802 (1904); Ann. chim. phys. (8) 10, 450 (1907).
2. Bougault u. Allard: Compt. rend. 135, 796 (1902).
3. Denigès: Ann. chim. phys. (8) 18, 168 (1909).
4. Fiesselmann: Chem.-Ztg. 1931, 490.
5. Fischer: Ber. 26, 633 (1893).