1. A. H. E. Griffiths, Nature
158, 670 (1946).
2. D. Hollis and P. W. Selwood, J. Chem. Phys. 35, 378 (1961).
3. B. Herpin, Théorie du Magnétisme, PUF, Paris (1968).
4. C. H. Morrish, The Physical Principle of Magnetism, John Wiley and Sons, New York (1965).
5. D. E. Patton, in: Magnetic Oxides ( D. J. Craik, ed.) John Wiley and Sons, New York (1975), p. 575.