1. M.H. Brodsky (ed.), Amorphous Semiconductors, 2nd edn, Topics Appl. Phys., Vol. 36 ( Springer, Berlin, Heidelberg 1985 )
2. R.K. Bullough, P.J. Caudrey (eds.), Solitons, Topics Curr. Phys. Vol. 17 ( Springer, Berlin, Heidelberg 1980 )
3. W.E. Spear, P.G. Le Comber, A.J. Snell, Philos. Mag. B 38, 303 (1978)
4. G.A.N. Connell, R.A. Street, Handbook on Semiconductors, Vol. 3 ( North Holland, Amsterdam 1980 ) p. 689
5. H. Me11. Amorphous and Liquid Semiconductors, ed by J. Stuke, W. Brenig ( Taylor and Francis, London 1974 ) p. 203