1. A.H. Wilson, Theory of Metals, 2nd ed. (Cambridge University Press, London, 1953), pp. 50–51.
2. R. Becker, Theorie der Elektrizität, Vol. 2 (Teubner, Berlin, 1933), Sec. 56; see also Ref. 3, p. 194.
3. N.W. Ashcroft and N. D. Mermin, Solid State Physics (Saunders, Philadelphia, 1976), pp. 213–235.
4. G.H. Wannier, Elements of Solid State Theory (Cambridge University Press, London, 1960), pp. 190–194.
5. W.A. Harrison, Solid State Theory (Dover, New York, 1979), pp. 64–71.