1. See, for example, Proc. of the International Conference on Localization, Interaction and Transport Phenomena, ed. G. Bergmann and Y. Bruynseraede, (Springer-Verlag, New York, 1985).
2. K.A. Chao, R Riklund, and A. Ferreira da Silva, Phys. Rev. B, 21, 5745, (1980).
3. N. F. Mott and E. A. Davis, Electronic Processes in Non-Crystalline Solids. (Oxford University Press, London, 1979).
4. V. J. Goldman, M Shayegan, and H. D. Drew, Phys. Rev. Letters 57, (1986).
5. V. J. Goldman, H. D. Drew, M Shayegan, and D. A. Nelson, Phys. Rev. Letters 56, 968 (1986).