1. T. Kasuya: in Magnetism, ed. by G. T. Rado and H. Suhl (Academic Press, New York 1966) vol. IIB, p. 215
2. For a review see: G. T. Rado and H. Suhl (ed) Magnetism (Academic Press, New York 1973) vol. V
3. Valence Instabilities and Related Narrow-Band Phenomena, ed. By R. D. Parks ( Plenum Press, New York 1977 )
4. Valence Fluctuations in Solids, ed. by L. M. Falicov, W. Hanke and M. B. Maple ( North-Holland, Amsterdam 1981 )
5. Valence Instabilities, ed. by P. Wachter and H. Boppart ( North- Holland, Amsterdam 1982 )