1. H. M. Ledbetter, unpublished studies, Cryogenics Division, NBS Institute for Basic Standards, Boulder, Colorado.
2. E. R. Naimon, H. M. Ledbetter, and W. F. Weston, J. Mater. Sci.
10:1309 (1975).
3. D. T. Read and H. M. Ledbetter, J. Eng. Mater. Technol.
99:181 (1977).
4. W. F. Weston and H. M. Ledbetter, in Ultrasonic Symposium Proceedings, IEEE 75Ch8994-4SU, New York (1975), p. 623.
5. H. M. Ledbetter, Metall. Trans.
8A:1006 (1977).