1. Petroff, J., Thiry, P.: Appl. Opt.19, 3957 (1980)
2. Hüfner, S.: Topics in Applied Physics. Ley, L., Cardona, M. (eds.), Vol. 27, p. 173. Berlin, Heidelberg, New York: Springer Verlag 1979
3. Mackintosh, A.R., Andersen, O.K.: In: Electrons at the Fermi Surface. Springford, M. (ed.). Cambridge: Cambridge University Press 1980
4. Jepsen, O., Glötzel, D., Mackintosh, A.R.: Phys. Rev. B (to be published)
5. Burdick, G.A.: Phys. Rev.129, 138 (1963)