1. Butti, K., and Perlin, J., 1980, A Golden Thread: 2500 Years of Solar Architecture and Technology, Cheshire Books, Von Nostrand Reinholdt Co., New York.
2. Gas Appliance Manufacturer’s Association, 2003, Statistical Highlights Ten Year Summary, 1991–2001, GAMA, Arlington, VA http://www.gamanet.org.
3. Battles, S. J., and Burns, E. M., 2000, Trends in Building-Related Energy and Carbon Emissions: Actual and Alternate Scenarios, American Council for an Energy-Efficient Economy, Summer Study on Energy Efficiency in Buildings.
4. Bureau of Economic Analysis, Industry Accounts Data, 2002, Gross Domestic Product by Industry, http://www.bea.gov/bea/dn2/gpox.htm.
5. U.S. Department of Energy, 2002 Buildings Energy Databook, http://www.btscoredatabook.net.