1. Andreyevskii, A. I., Nabitovitch, I. D. and Voloshchuk, Ya. V., (1960), Kristallograflya, 5, 369
2. (1961), Kristallografiya, 6, 662
3. (1962), Kristallograflya, 7, 865.
4. Azaroff, L. V., (1963), Rev. Mod. Phys., 35, 1012.
5. Badzian, A. R., (1967), Mater. Res. Bull., 2, 987.