1. E. Steinort, Proc. 3rd Eur. Conf. Hard Magn. Mater., Amsterdam, 1974, p. 66.
2. G. Fagherazzi, Ceramurgia 6 (1976) 26.
3. M. McCaig, Permanent Magnets in Theory and Practice (John Wiley & Sons, New York, 1977 ) Vol. 1, p. 1.
4. M. J. Ruthner, H. G. Richter, and I. L. Steiner, Ferrites, eds. Y. Hoshino, S. Iida, and M. Sugimoto ( University of Tokyo Press, Tokyo, 1971 ) p. 75.
5. M. J. Ruthner, O. Ruthner, Iron Steel Eng. Nov. (1979) 36.