1. 1P. Popper, and P. Popper ; pp. 209 -19, in Special Ceramics I . British Ceramics Research Association, Stoke-on-Trent, England, 1960 .
2. 2(a)H. Sato, S. Shinozaki, M. Yessik, J. E. Noakes, R. C. Marshall, J. W. Faust, and C. E. Ryan ; pp. 222 -29, in Silicon Carbide-1973 . University of South Carolina Press, Columbia, S.C., 1974 . A detailed description of earlier work of the present authors on this subject is found in: