1. 1) W.M.Thomas et al. : International Patent Appl.No.PCT/GB92/02203.
2. 2) H. Okamura, K. Aota, Y. Sakamoto, M. Esumi and K. Ikeuti : Behavior of oxide during friction stir welding of aluminum alloy and its influence on mechanical properties, Quarterly Journal of the Japan welding Society, 19-3 (2001), 446-456. (in Japanese)
3. 3) M. Enomoto : Application of friction stir welding for aluminum alloys, Journal of light metal welding & construction, 36-2 (1998) 75-79. (in Japanese)
4. 4) M. Kumagai and S. Tanaka : Application of friction stir welding to welded construction of aluminum alloys, Journal of light metal welding & construction, 39-1 (2001), 22-28. (in Japanese)
5. 5) H. Okamura : Character of friction stir welding and application in Japan, Journal of the Japan welding society, 69-7 (2000), 565-571. (in Japanese)