1. K. C. Sales and R. Viswanathan, J. Low Temp. Phys. 23, 449 (1976).
2. M. N. Groshev, M. D. Koterlin, E. M. Levin, R. V. Lutsiv, N. M. Miftakhov, Yu. P. Smirnov, A. E. Sovestnov, A. V. Tyunis, V. A. Shaburov, R. I. Yasnitskii, S. M. Kuz’mina, V. I. Petrova, and V. A. Tyukavin, Fiz. Tverd. Tela (Leningrad) 28, 2711 (1986) [Sov. Phys. Solid State 28, 1519 (1986)].
3. J. Rohler, in Handbook of the Physics and Chemistry of Rare Earths, K. A. Gschneider, Jr. and L. Eyring (eds.), North-Holland, Amsterdam (1988), Vol. 10, p. 453.
4. E. A. Goremychkin and R. Osborn, Phys. Rev. B 47, 14 280 (1993).
5. E. A. Goremychkin, A. Yu. Muzychka, and R. Osborn, Physica B 179, 184 (1992).