1. 1) H. Masumoto and H. Saitô: J. Japan Inst. Metals, 6 (1942), 123;
2. H. Masumoto and H. Saitô: J. Japan Inst. Metals, 12, No. 5 (1948), 6;
3. H. Masumoto and H. Saitô: Sci. Rep. RITU., A4 (1952), 321.
4. 2) C. W. Lufcy and W. T. Heath: Electronics, (1955) June, 137.
5. 3) H. Saitô: J. Japan Inst. Metals, B-14, No. 5 (1950), 17;