1. Burzo, E.: Proc. X-th Rare Earth Research Conf. Arizona 1973, p. 96.
2. Burzo, E., Lazar, D.P.: C.R. Acad. Sci. B 276 (1973) 239.
3. Hilscher, G., Rais, H., Kirchmayr, H.R.: Phys. Status Solidi (b) 59 (1973) K 5.
4. Ilarraz, J., Del Moral, A.: Phys. Status Solidi (a) 57 (1980) 89.
5. Burzo, E.: Proc. X-th Rare Earth Research Conf. Arizona 1973, p. 96.