http://ja.wikipedia.org/wiki/%E6%8C%81%E7%B6%9A%E5%8F%AF%E8%...
http://www.eic.or.jp/ecoterm/?act=view&serial=1132
http://www.apec-vc.or.jp/apec_j/hint/ecobusiness/page03.html
http://www005.upp.so-net.ne.jp/yoshida_n/L14_00.htm
http://www.econavi.org/chikyu/jizoku01.html