1. H.B.G. Casimir, Magnetism and Very Low Temperatures, (Dover, New York, 1961); also H.B.G. Casimir and F.K. du Pre, Physica 5, 507 (1938)
2. C.J. Gorter, Paramagnetic Relaxation, (Elsevier, Amsterdam, 1947)
3. A.H. Morrish, The Physical Principles of Magnetism, (Wiley, New York, 1965), Chapter 3
4. K.J. Standley and R.A. Vaughan, Electron Spin Relaxation Phenomena in Solids, (Plenum, New York, 1969), pp. 10–14
5. C.B.P. Finn, R. Orbach, and W.P. Wolf, Proc. Phys. Soc. (London) 77, 261 (1961)