1. J. W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry. Longmans, London, 1927, Vol. 2, p. 795.
2. A. Baranski andM. Goras, Chemia Stosowana 4A (1966) 401.
3. W. Garner, Chemistry of the Solid State (W. Garner, ed.). Butterworths Scientific Publications, London, 1955, p. 213.
4. P. Jacobs andF. Tompkins, ibid., p. 184.
5. W. Garner, ibid., p. 232.