1. J. Tauc, in “Optical Properties of Solids”, p.279, F. Abeles ed., North-Holland Publ. Co., 1972; also in “Amorphous and Liquid Semiconductors”, Chapter 4, J. Tauc ed., Plenum Press, 1974.
2. N.F. Mott and E.A. Davis, “Electronic Processes in Non-Crystalline Ma terials”, 1979 Oxford University Press.
3. H. Fritzsche, Solar Energy Materials 3, 447 (1980).
4. G.A.N. Connell, in “Amorphous Semiconductors”, Topics in Applied Physics vol. 36, M.H. Brodsky ed., Springer-Verlag, 1979.
5. G.D. Cody, in “Semiconductors and Semimetals”, Vol.2IB, p. 11, J. Pankove ed., Academic Press, 1984.