1. http://www.nap.edu/openbook.php?record_id=13152
2. Smart Growthhttp://www.epa.gov/smartgrowth/
3. County Health Rankingshttp://www.countyhealthrankings.org
4. The SustainLane U.S. City Rankings. How Green is Your City?;Kalenzig,2007
5. Urban Environment Reporthttp://files.earthday.net/UER/report/