1. Shirota, N. N., Pashintsev, Y. I.: Dokl. Akad. Nauk SSSR 127 (1959) 609; as cited in [77M1].
2. Sirota, N. N., Olekhnovich, N. M.: Dokl. Akad. Nauk SSSR 136 (1961) 879 and 143 (1962) 370; as cited in Sirota, N. N.: Acta Crystallogr. A 25 (1969) 223 and in [77M1, 92S1].
3. Arnold, G., Nereson, N.: Phys. Rev. 131 (1963) 2098.
4. Cromer, D. T., Mann, J. B.: Acta Crystallogr. A 24 (1968) 321.
5. Beilin, V. M., Vekilov, Yu. Kh., Krasil’nikov, O. M.: Fiz. Tverd. Tela 10 (1968) 3101; Sov. Phys. Solid State 10 (1969) 2443 (English Transl.).