1. 1) M. Nanjo: Bulletin of the Research Institute of Mineral Dressing and Metallurgy, Tohoku University, vol. 43, No. 2 (19880325), (1988) pp. 239–251.
2. 2) K. Halada: Press Release of National Institute for Materials Science, 11 Jan. 2008 (http://www.nims.go.jp/jpn/news/press/pdf/press215.pdf).
3. 3) S. Bringezu, H. Schütz, S. Steger and J. Baudisch: Ecological Economics 51 (2004) 97–124.
4. 4) A. Adriaanse, S. Bringezu, A. Hammond, Y. Moriguchi, E. Rodenburg, D. Rogich and H. Schütz: Resources Flows: The Material Basis of Industrial Economies, (World Resources Institute, Washington, D.C., April, 1997).
5. 5) K. Halada, K. Ijima, N. Katagiri and T. Okura: J. Jpn. Inst. Metals 65 (2001) 564–570.