1. Carbon-Nitrogen-Sulfur
2. U.S. Environmental Protection Agency.Inventory of U.S. greenhouse gas emissions and sinks: 1990-2008;EPA, Office of Atmospheric Programs (6207J): Washington, DC,2010. URLhttp://epa.gov/climatechange/emissions/usinventoryreport.html(Accessed 18 May 2010; verified 18 May 2010).