1. Computer-Based Global Models: From Early Experiences to Complex Systems
2. Ewing, B., Moore, D., Goldfinger, S., Oursler, A., Reed, A. & Wackernagel, M. (2010). The Ecological Footprint Atlas 2010. Oakland: Global Footprint Network.
3. Groningen Growth and Development Centre. (2010). Madison Project Retrieved 13 July 2014