1. 1) Biomass Nippon, home page, http://www.maff.go.jp/biomass/index.htm
2. Cone structure of hexagonal carbon sheets stacked in wood cell lumen
3. 4) T. Suzuki, A. Takahashi, E. Kuwahara, T. Yamada and T. Homma, “Hydrogasification of wood for high heating-value gas production IV.”, Mokuzai Gakkaishi, Vol.33, No.5, pp.423-429 (1978).