1. 1) Japan Oil, Gas and Metals National Corporation: Stockpiling, ‹http://www.jogmec.go.jp/english/activities/stockpiling_metal/index.html›, (2007/8/1).
2. 2) Ministry of Economy, Trade and Industry: Yearbook of Iron and Steel, Non-ferrous Metals, and Fabricated Metals Statistics, (2006).
3. 3) Japan Oil, Gas and Metals National Corporation: Material Flow of Mineral Resource 2005 (in Japanese), (2006).
4. 4) Rare Metal Association: Rare Metals Shikihou (in Japanese), (2007).
5. 5) M. Shimada, K. Ijima, Y. Sawatani, K. Nakajima, T. Nagasaka, T. Tsukihashi, Y. Moriguchi and K. Halada: New Trend of Material Flow in the Era of Globalization, Advances in Ecomaterials (Proc. of 7th Int. Conf. on Ecomaterials), Stallion Press, Singapore, (2005), 620.