1. Metals Handbook, 8th ed., vol. 1, p. 1220, American Society for Metals, Metals Park, Ohio, 1961.
2. K. C. Li:Rare Metals Handbook, C. A. Hampel, ed., p. 596, Reinhold, New York, 1961.
3. G. J. Dooley III and T. W. Haas:J. Metals, 1970, vol. 22, no. 11, pp. 17–24.
4. H. L. Marcus and P. W. Palmberg:Trans. TMS-AIME, 1969, vol. 245, pp. 1664–66.
5. G. J. Dooley III and T. W. Haas:J. Vac. Sci. Technol, 1970, vol. 7, pp. 92–100.