1. 1) Homepage of Ministry of Health, Labour and Welfare, http://www.mhlw.go.jp.
2. 2) M. Niinomi: Recent Biocompatibility Metallic Materials, Structural Biomaterials for the 21st Century, ed. by M. Niinomi, T. Okabe, E. M. Taleff, D. R. Lesuer and H. E. Lippard, (TMS, Warrendale, 2001) pp. 3–14.
3. 3) C. Baker: Metal Science Journal 5 (1971) 92–100.
4. 4) Private Communication of Mr. Ito of JTA.
5. 5) T. Tomonari: Titanium Industry—Its Growing Steps and Future Possibilities, (The Japan Titanium Assaciation, 2001), pp. 80–82.