Columbia subject headings:
Coal gasification--Research--United States.
Coal--Combustion--Research--United States.
Coal-fired power plants--Research--United States.
Electric power-plants--Environmental aspects.
Harvard subject headings:
Coal gasification--Research--United States.
Coal--Combustion--Research--United States.
Coal-fired power plants--Research--United States.
Electric power-plants--Environmental aspects
Princeton subject headings:
Coal gasification--Research--United States.
Coal--Combustion--Research--United States.
Coal-fired power plants--Research--United States.
Electric power-plants--Environmental aspects.