1. Valency Instabilities. Proc. Int. Conf. held in Zurich, April 13–16, 1982, eds. P. Wachter and H. Boppart (North Holland).
2. Coqblin, B. and Blandin, A., 1968, Adv. in Phys. 17. pp. 281.
3. Anderson, P.W., 1981, in Valency Fluctuations in Solids (Santa Barbara Conference, North Holland), p. 451.
4. Mott, N.F., 1982, Ref. 1, p. 403.
5. Crabtree, G.W., Johanson, W.R., Edelstein, A.S. and McMasters, O.D., 1981, ref. as in ref (3), p. 93.