1. Wernick, J.H., Geller, S.: Trans AIME218, 866 (1960)
2. Williams, H.J., Wernick, J.H., Nesbitt, E.A., Sherwood, R.C.: J. Phys. Soc. Jpn.17 (Suppl. B 1), 91 (1962)
3. Kirchmayr, R., Poldy, A.: Handbook on the Physics and Chemistry of Rare Earths. Gschneidner, K.A., Eyring, LeR. (eds.), Vol. 2, p. 55. Amsterdam: North-Holland 1979
4. Hill, T.W., Wallace, W.E., Craig, R.S., Inoue, T.: J. Solid State Chem.8, 364 (1973)
5. Barbara, B., Rossignol, M.F., Boucherle, J.X.: Phys. Lett.55A, 321 (1975)