1. See for example, M. Born and E. Wolf, ‘Principles of Optics’ (Pergamon Press, Oxford, 6th ed. 1980) p. 327.
2. E. D. Pierron, D. L. Parker and J. B. McNeely, Acta Crystallogr 21, 290 (1966).
3. M. Cardonna, Atomic Structure and Properties of Solids, E. Burstein Ed. (Academic Press, New York, 1972) p. 514.