1. B.H. Justice and E.F. Westrum, Jr., J. Phys. Chem., 67:339 (1963); ibid, 67:345 (1963).; ibid., 67:659 (1963).
2. B.H. Justice, E.F. Westrum, Jr., E. Chang, and R. Radebaugh, ibid.., 73: 333 (1969).
3. J.T. Hougen and S. Singh, Proc. Roy. Soc., (London). A277:193 (1964); Phys. Rev. Lett., 10: 406 (1963).
4. J.D. Axe, Phys. Rev., A42:136 (1964); see also R. J. Elliott and R. Loudon, Phys. Lett., 3: 189 (1963).
5. J.B. Gruber, “Pre. 9th Rare Earth Research Conf.” Blacksburg, VA, October 10–14, 1971, pp. 465–478 NTIS, U.S. Dept. of Commerce, Springfield, VA 22151.