1. K. N. Strafford, Met. Rev. No. 138,Met. Mater. 3, 409 (1969).
2. D. J. Young:Rev. High Temp. Mater. 4, 299 (1980).
3. A. E. Goresy and G. Kullerud,Carn. Inst. Washington Yearb. 62, 182 (1963).
4. K. T. Jacob, D. B. Rao, and H. G. Nelson,Oxid. Met. 13, 25 (1979).
5. Wen-Ta Tsai, Master's thesis of the University of Wisconsin, Milwaukee (1979).