1. J.M. Daniels, Proc. Phys. Soc. (London) A
66, 673 (1953).
2. H.B.G. Casimir and F.K. du Pré, Physica
5, 507 (1938).
3. C.J. Gorter, Paramagnetic Relaxation, Elsevier, New York (1947).
4. C.J. Gorter, in Fluctuation, Relaxation and Resonance in Magnetic Systems, D. ter Haar, ed., Plenum Press, New York (1962), p. 87.
5. A.T. Skjeltorp and W.P. Wolf, in AIP Conf. Proc., No. 5, p. 695 (1972).