1. Gmelin Handbook of Inorganic Chemistry, System no. 39, vol. C6, Springer, Berlin, New York, 1982.
2. J.D. Corbett, in: G. Meyer, L.R. Morss (Eds.), Synthesis of Lanthanide and Actinide Compounds, Kluwer Academic Publishers, Dordrecht, 1991, p. 159.
3. G. Meyer, M.S. Wickleder, in: K.A. Gschneidner Jr., L. Eyring (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 28, Elsevier Science, 2000 (Chapter 177).
4. Reduced halides of the rare-earth elements