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3. D. W. Jones, S. P. Farrant, D. Fort and R. G. Jordan, p. 11 in “Rare Earths and Actinides 1977”, Inst. Phys. Conf. Ser. No. 37, Institute of Physics, Bristol (1 978).
4. B. J. Beaudry and K. A. Gschneidner, Jr., p. 173 in “Handbook on the Physics and Chemistry of Rare Earths,” Vol. 1, K. A. Gschneidner, Jr. and L. Eyring, eds. North-Holland Publishing Co., Amsterdam (1978).