1. I. Mayer, J. Cohen and I. Felner: Acta Crystallogr. A, Vol. 28 (1972), p. S102.
2. I. Felner and I. Nowik: J. Phys. Chem. Solids, Vol. 39 (1978), p.767.
3. V. F. Terekhova, P. I. Kripyakevich, D. P. Frankevich and R. S. Torchinova: Izv. Akad. Nauk SSSR, Met. (1967), No. 1, p.205; English translation in Russ. Met. (1967), No. 1, p.107.
4. G. A. Costa, E. A. Franceschi and A. Tawansi: J. Less-Common Met., Vol. 106 (1985), p.175.
5. J. W. Ross and S. P. Walley, in: Rare Earths and Actinides, 1977, edited by W. D. Corner, B. K. Tanner, Institute of Physics, Conference Series, No. 37 (The Institute of Physics, Bristol 1978), p.155.