1) M. Zhang, D. Ma, X. Jiang, and S. Liu: Proc. 8th Int. Workshop on RE Magnets, p. 541, Univ. Dayton. Dayton (1985).
2) X. Xiao, K. J. Strnat, H. F. Mildrum,and A. E. Ray: Proc. 9th Int. Workshop on RE Magnets, p. 467, Deutsche Physicalische Geselschaft, Bad Honnef (1987).
3) M. Tokunaga, H. Kogure, M. Endoh, and H. Harada: IEEE Trans. Magn., MAG-23, 2287 (1987).