Columbia subject headings:
Coal mines and mining--Government policy--Colombia--Ejón Hill Region.
Coal trade--Government policy--Colombia--Ejón Hill Region.
Harvard subject headings:
Coal mines and mining--Government policy--Colombia--Ejón Hill Region.
Coal trade--Government policy--Colombia--Ejón Hill Region.
Princeton subject headings:
Coal mines and mining--Government policy--Colombia--Ejón Hill Region.
Coal trade--Government policy--Colombia--Ejón Hill Region.