1. 1) Y. Fukai, K. Tanaka and H. Uchida: Suiso-to-Kinzoku, (Uchida Rokakuho Publishing Co., Ltd., Tokyo, 1998).
2. 2) M. Nagumo: Fundamentals of Hydrogen Embrittlement, (Uchida Rokakuho Publishing Co., Ltd., Tokyo, 2008).
3. 3) S. Matsuyama: Delayed Fracture, (The Nikkan Kogyo Shimbun Ltd., Tokyo, 1973).
4. 4) T. Kushida, H. Matsumoto, N. Kuratomi, T. Tsumura, F. Nakasato and T. Kudo: Tetsu-to-Hagané 82 (1996) 297-302.
5. 5) S. Yamasaki and T. Takahashi: Tetsu-to-Hagané 83 (1997) 454-459.