Columbia subject headings:
Coal mines and mining--Safety regulations--United States.
Coal trade--Government policy--United States.
Coal--Environmental aspects--Government policy--United States.
Harvard subject headings:
Coal mines and mining--Safety regulations--United States
Coal trade--Government policy--United States.
Coal--Environmental aspects--Government policy--United States.
Princeton subject headings:
Coal mines and mining--Safety regulations--United States.
Coal trade--Government policy--United States.
Coal--Environmental aspects--Government policy--United States.