1. H. Morton and H. C. Bolton, Chem. News,28, 1873.
2. H. Bremer, Z. anorg. Chem.,1, 112, 1892.
3. H. C. Jones and W. W. Strong, Am. Chem. J.,43, 37, 97, 1910;45, 1, 113, 1911;47, 27, 126, 1912.
4. H. C. Jones and J. S. Guy, Am. Chem. J.,49, 1, 1913.
5. V. L. Levshin, Izv. AN SSSR, ser. fiz. no. 2, 185, 1937; no. 3, 337, 1938.