1. 1) J. Smit and H. P. J. Wijin: Ferrites, Philips Technical Library, Eindhoven, (1970), p. 177.
2. 2) H. Newman and H. P. J. Wijin: J. Amer. Soc., 51 (1968), 536.
3. 3) B. T. Shirk and W. R. Buessem: J. Appl. Phys., 40 (1969), 1294.
4. 4) J. J. Went, G. W. Rathenau, E. W. Gorter and G. W. van Oosterhout: Philips Technic. Rev., 13 (1952), 194.
5. 5) G. Albanese and G. Asti: IEEE. Trans. Mag., MAG-6 (1970), 58.