1. V.M. Goldschmidt, Skrifter Norski Videnskaps-Akad, OSLO I, Mat. Naturv, Kl, No. 8 (1926).
2. M.E. Straumanis and A. Dravnieks, J. Am. Chem. Soc., 71 (1949), p. 683.
3. M. Kestigian, J.G. Dickinson and R. Ward, ibid, 79 (1957), p. 5578.
4. M. Kestigian and R. Ward, ibid, 76, (1954), p. 6024.
5. F. Galasso, Structure and Properties of Inorganic Solids, Pergamon Press, NY, 1970. Japanese Translation, Agne Gijutsu Center Co., Tokyo, 1984.