1. H. A. Kramers, Physica, 1, 182 (1934).
2. J. B. Goodenough, Phys. Rev., 100, 545 (1955).
3. J. B. Goodenough, Magnetism and the Chemical Bond, Interscience, Wiley, New York (1963).
4. J. Kanamori, J. Phys. Chem. Solids, 10, 87 (1959).
5. P. W. Anderson, in: Solid State Physics, F. Seitz and D. Turnbull (eds.), 14, 99–214, Academic Press, New York (1963).