1. American Gas Association,An Evaluation of Alternative Control Strategies to Remove Sulfur Dioxide, Nitrogen Oxides and Carbon Dioxide at Existing Large Coal-Fired Facilities, EA-1989-1, January 13,1989,30 pp.
2. American Gas Association, natural gas substitution forecasts, telephone conversationwith Nelson Hay.
3. American Gas Association, “Natural Gas Price Forecasts”, TERA 1989 MidYear Base Case Forecast.
4. Bohi, Douglas, and Mary Beth Zimmerman, “An Update on Econometric Studies of Energy Demand Behavior,” Annual Review of Energy, 1984, pp.127–149.
5. Data Resources Inc., Coal Market Forecasts, 1989.