1. 1) Y. Murakami: Metal Fatigue: Effects of Small Defects and Nonmetallic Inclusions, Elsevier Science, Amsterdam, (2002), 75.
2. 2) A. Adachi, H. Shoji, A. Kuwabara and Y. Inoue: Denki Seiko, 46 (1975), 176 (in Japanese).
3. 3) S. Nishijima, E. Suzuki, A. Morii, T. Obata, K. Uchibori, Y. Niikura, K. Nisawa, J. Koarai and Y. Itoh: Trans. Jpn. Soc. Spring Eng., 32 (1987), 52 (in Japanese).
4. 4) Ultrasonic Inspection for Various Products and Structures, The Japanese Society for Non-destructive Inspection, Tokyo, (1989), 42 (in Japanese).
5. 5) Ultrasonic Testing III, The Japanese Society for Non-destructive Inspection, Tokyo, (2001), 71 (in Japanese).