LSA Colorado University.edu. (n.d.). Natural Gas. Retrieved December 22, 2009, from Natural Gas: http://lsa.colorado.edu/essence/texts/naturalgas.htm
Propane 101. (2009). Propane Vs. Natural Gas. Retrieved December 22, 2009, from Promoting Propane Safety Through Better Understanding: http://www.propane101.com/propanevsnaturalgas.htm
Stoves Only. (2009). What is BTU? Retrieved December 22, 2009, from Stoves Only: http://www.stoves-only.com/fuel-comparison-table
U.S. Department of Energy. (2009, November 12). Alternative and Advanced Fuels: Propane. Retrieved December 22, 2009, from Energy Efficiency and Renewable Energy: http://www.afdc.energy.gov/afdc/fuels/propane.html
U.S. Department of Energy. (2009, August 17). Alternatve and Advanced Fuels: Natural Gas. Retrieved December 22, 2009, from Energy Efficiency and Renewable Energy: http://www.afdc.energy.gov/afdc/fuels/natural_gas.html
U.S. Energy Information Administration. (n.d.). Natural Gas Explained. Retrieved December 22, 2009, from U.S. Energy Information Administration: http://tonto.eia.doe.gov/energyexplained/index.cfm?page=natural_gas_factors_affecting_prices
U.S. Energy Information Administration. (n.d.). Propane Explained. Retrieved December 22, 2009, from U.S. Energy Information Administration: http://tonto.eia.doe.gov/energyexplained/index.cfm?page=propane_factors_affecting_prices