1. Wertheim, G.K., Smith, N.V., Traum, M.M., Buchanan, D.N.E.: Phys. Lett.49A, 191 (1975)
2. For a review see C. Herring,Magnetism, (ed. by G.T. Rado and H. Suhl) Vol. IV. New York: Academic Press 1966
3. Kittel, C.: Introduction to Solid State Physics; IVth edition p. 254. New York: John Wiley & Sons, Inc. 1971
4. Nemoshkalenko, V.V., Aleshin, V.G., Kucherenko, Yu.N., Sheludchenko, L.M.: J. Electron Spectrosc.6, 145 (1975)
5. Mahan, G.D.: Phys. Rev.163, 612 (1967)