1. R. Bozio, A. Feis, D. Pedron, I. Zanon, and C. Pecile, this volume, and references therein.
2. “Proceedings of the International Conference on Science and Technology of Synthetic Metals (ICSM’88)”, ed. by M. Aldissi, Svnth, Metals 27: 1-99 (1988).
3. F. Wooten, “Optical Properties of Solids”, (Academic Press, New York, 1972).
4. P. F. Maldague, Phys. Rev. B 16: 2437 (1977).
5. W. Gasser and R. Höfling, Phys. stat. sol. (b) 92: 91 (1979).