1. The Shorter Oxford English Dictionary,1973
2. Our Ecological Footprint;Wackernagel,1996
3. WWF, Living Planet Report, WWF International, Gland, Switzerland, http://www.wwf.org.uk/-filelibrary/-pdf/livingplanet2002.pdf (accessed 14-1-05).
4. Sharing Nature's Interest;Chambers,2000
5. Factor 4;von Weizsacker,1997