1. G. J. Zimmer, L. Gal, and F. B. Humphrey, AIP Conf. Proc. 29, 85 (1976).
2. G. P. Vella-Coleiro, IEEE Trans. Magn. 13(5), 1163 (1977).
3. A. M. Balbashov, P. I. Nabokin, A. Ya. Chervonenkis, and A. P. Cherkasov, Fiz. Tverd. Tela (Leningrad) 19(6), 1881 (1977) [Sov. Phys. Solid State 19, 1102 (1977)].
4. V. G. Kleparskii and V. V. Randoshkin, Fiz. Tverd. Tela (Leningrad) 21(2), 416 (1979) [Sov. Phys. Solid State 21, 247 (1979)].
5. A. G. Shishkov, V. V. Grishachev, E. N. Il’icheva, and Yu. N. Fedyunin, Fiz. Tverd. Tela (Leningrad) 30(8), 2257 (1988) [Sov. Phys. Solid State 30, 1303 (1988)].