1. For example, see Adler, D. et al. 1978, Rev. Mod. Phys. 209.
2. Henisch, H.K., Smith, W.R. and W. Wihl, in Amorphous and Liquid Semiconductors, Eds. J. Stuke and W. Brenig, pp. 567 (1973) Taylor & Francis, London.
3. Smith, W. and Henisch, H.K., Phys. Stat. Sol. (a) 17, K81 (1973).
4. Homma, K., Henisch, H.K. and Ovshinsky, S.R. J. Noncryst. Solids. 25 & 1105 (1980).
5. Marshall, J. and Owen, A.E. Phys. Stat. Sol. (a) 12, 181 (1972).