1. H. Fritzsche, Amorphous and Liquid Semiconductors, ed. J. Taue, Plenum Press, Chapter 5 (1973).
2. W. Paul, Proc. 11th Intl. Conf. on Physics of Semi-conductors, Warsaw (1972), p. 38.
3. H. Mell, Proc. 5th Intl. Conf. on Amorphous and Liquid Semiconductors, Garmisch-Partenkirchen (1973), P. 203.
4. W. E. Spear, Proc. 5th Intl. Conf. on Amorphous and Liquid Semiconductors, Garmisch-Partenkirchen (1973), P. 1.
5. M. H. Cohen, H. Fritzsche and S. R. Ovshinsky, Phys. Rev. Letts 22, 1065 (1969).