1. Valence fluctuation phenomena
2. A. Jayaraman, in: K.A. Gschneidner Jr., L. Eyring (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 2, ch. 20, North-Holland, Amsterdam, 1979.
3. M. Loewenhaupt, K.H. Fischer, in: K.A. Gschneidner Jr., L. Eyring (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 16, ch. 105, Elsevier, Amsterdam, 1993.
4. P. Wachter, in: K.A. Gschneidner Jr., L. Eyring, G.H. Lander, G.R. Choppin (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 19, ch. 132, Elsevier, Amsterdam, 1994.
5. D. Jaccard, J. Sierro, in: P. Wachter, H. Boppart (Eds.),Valence Instabilities, North-Holland, Amsterdam, 1982, p. 409.