1. See, for example, B.C. Sales, Handbook on the Physics and Chemistry of Rare Earths, edited by K.A.G. Jr, J.C.G. Bunzli, V.K. Pecharsky (Elsevier Science BV, Amsterdam, 2003), Vol. 33, p. 1
2. G.S. Nolas, J.L. Cohn, G.A. Slack, S.B. Schujman, Appl. Phys. Lett. 73, 178 (1998)
3. S.J. Poon, Seminod. Semimet. 70, 37 (2001)
4. I. Terasaki, Y. Sasago, K. Uchinokura, Phys. Rev. B 56, R12685 (1997)
5. G.A. Slack, Thermoelectric Handbook (Boca Raton, FL, CRC, 1995), p. 407