1. Martin R.L., (1968) New Pathways in Inorganic Chemistry, Ebsworth E.A.V., Maddock A.G., and Sharpe A.G., Eds., Cambridge University Press, London, Chapter 9
2. Anderson P.W., (1963) Magnetism, (Rado G.T. and Suhl H., Eds), Vol. 1, p. 25, Academic Press, Inc., New York; Stevens K.W.H., Phys. Reports (Phys. Lett. C) 24C,, #1, February, 1976
3. Carrington A. and McLachlan A.D., (1967) Introduction to Magnetic Resonance, Harper and Row, New York
4. Smart J.S., (1965) Magnetism, (Rado G.T. and Suhl H., Eds), Vol. Ill, p. 63, Academic Press, Inc., New York
5. Friedberg S.A. and Raquet C.A., J. Appl. Phys. 39,, 1132 (1968)