1. A. R. PATEL and A. VENKATESHWARA RAO,Bull. Mater. Sci. 4 (1982) 527.
2. P. H. EGLI and L. R. JOHNSON, ?Arts and Science of Growing Crystals?, edited by J. J. Gilman (Wiley, New York, 1970).
3. K. NAKAMOTO, ?Infrared Spectra of Inorganic and Coordination Compounds? (Wiley, New York, 1970).