1. Loos J., phys. stat. sol. (b)56 (1973), K 51.
2. Loos J., Czech. J. Phys.B 23 (1973), 952.
3. Loos J., Int. Conf. on Magnetism, Moscow (1973), in print.
4. Abramowitz M., Stegun I. A., Handbook of Mathematical Functions, Chap. 7, Dover Publication Inc., New York, 1968.