United States. Environmental Protection Agency. Office of Transportation and Air Quality. Assessment and Standards Division. (2011). Greenhouse gas emissions model (GEM) user guide. Assessment and Standards Division, Office of Transportation and Air Quality, U.S. Environmental Protection Agency.
Chicago Style (17th ed.) CitationUnited States. Environmental Protection Agency. Office of Transportation and Air Quality. Assessment and Standards Division. Greenhouse Gas Emissions Model (GEM) User Guide. [Washington, D.C.]: Assessment and Standards Division, Office of Transportation and Air Quality, U.S. Environmental Protection Agency, 2011.
MLA (9th ed.) CitationUnited States. Environmental Protection Agency. Office of Transportation and Air Quality. Assessment and Standards Division. Greenhouse Gas Emissions Model (GEM) User Guide. Assessment and Standards Division, Office of Transportation and Air Quality, U.S. Environmental Protection Agency, 2011.