1. For a review, see, for example, “Fundamental Physics of Amorphous Semiconductors”, edited by F. Yonezawa, Springer-Verlag, Berlin, 1981.
2. Ref. 1, M. Brodsky, p. 56.
3. G. E. Pake, J. Chem Phys. 16, 327 (1948).
4. A. Abragam, “The Principles of Nuclear Magnetism”, Oxford University Press, London (1961), p. 216–223.
5. I. J. Lowe and R. E. Norberg, Phys. Rev. 107, 46 (1957).