1. Gottfried, C. and Schusterius, C.Zeit. Krist., 1933,84, 65.
2. Mooney, R. C. L.Phys. Rev., 1931,37, 1306.
3. Wyckoff, R. W. G.The Structure of Crystals, 1935, Reinhold.
4. Ramaseshan, S., Venkatesan, K. and Mani, N. V.Proc. Ind. Acad. Sci., 1957,46 A, 95.
5. Barker, Th. V.Zeit. Krist., 1907,43, 533.