1. M.R. Norman, D.D. Koelling, in: K.A. Gschneidner Jr, L. Eyring, G.H. Lander, G.R. Choppinin (Eds.), Handbook on the Physics and Chemistry of Rare earths, vol. 17, North-Holland, Amsterdam, 1978.
2. Science and Technology of Rare Earth Meterials,1980
3. H.E. Sliney, NASA Tech. Note NASA-TN-D-5301, (1969).