1. J. Staun Olsen, L. Gerward, U. Benedict and J.-P. Itié, Physica B 133, 129 (1985).
2. Y. C. Zhao and W. B. Holzapfel, J. Alloys Compounds 246, 216 (1997).
3. D. A. Koskenmaki and K. A. Gschneidner Jr., in Handbook on the Physics and Chemistry of Rare Earths, edited by K. A. Gschneidner Jr. and L. Eyring, North-Holland, Amsterdam, 1978, Chap. 4.
4. A. Jayaraman, Phys. Rev. 137, A179 (1965).
5. Ye. G. Ponyatovskii, Dokl. Akad. Nauk SSSR 120, 10221 (1958).