1. Nitrates: An Environmental Assessment,1978
2. Environmental Protection Agency,1981
3. Nitrogen Oxides;National Academy of Sciences,1977
4. Air Quality Criteria for Ozone and Other Photochemical Oxidants, EPA-600/8-78-004, April 1978.
5. Process Influencing the Concentration of Nitrogen Oxides in the Lower Troposphere, EF 78-31R3. Prepared for American Petroleum Institute by Systems Applications, Inc., July 1978.