1. Landolt-Bornstein, ?Crystal and Solid State Physics? Vol. 16b (Springer-Verlag, Berlin, Heildelberg, New York, 1982).
2. P. S. Peercy andG. A. Samara,Phys. Rev. B8 (1973) 2033.
3. D. K. Agrawal andC. H. Perry, in ?Light Scattering in Solids?, edited by M. Balkanski (Flammarion, Paris, 1971) p. 429.
4. H. Hammer,ibid.?, edited by M. Balkanski (Flammarion, Paris, 1971), p. 425.
5. Idem, in ?Advances in Raman Spectroscopy?, Vol. 1 (Heyden, London, 1972) p. 167.