1. R. M. Bozorth,Ferromagnetism, 4th printing (Van Nostrand, New York, 1956), p. 60.
2. K. Kono, T. Morimoto, T. Ishii, S. Yamada, H. Suzuki, and T. Omori, paper read at the sectional meeting of the Physical Society of Japan, Miyazaki, Oct. 1989, 14p-F3.