1. R. D. Goodwin and J. R. Purcell, in Advances in Cryogenic Engineering, Vol, 5, K. D. Timmerhaus (ed.), Plenum Press, Inc., New York (1960) p. 577.
2. I. Johnson unpublished data.
3. Smithells, Metals Handbooks Interscience Publishers, Inc. , New York (1949).
4. J. Morris, B. Schurin, and O. H. Olson, Thermodynamic and Transport Properties of Gases, Liquids, and Solids, McGraw-Hill Book Company, Inc. , New York (1959) p. 400.
5. Methods of Experimental Physics, Vol. 6, Part A, Academic Press, New York (1959) p. 393.