Columbia subject headings:
Coal mines and mining--Law and legislation--Compliance costs--Poland.
Coal mines and mining--Law and legislation--Compliance costs--United States.
Coal trade--Poland--Costs.
Coal trade--United States--Costs.
Coal--Taxation--Poland.
Coal--Taxation--United States.
Harvard subject headings:
Coal mines and mining--Law and legislation--Compliance costs--Poland.
Coal mines and mining--Law and legislation--Compliance costs--United States.
Coal trade--Poland--Costs.
Coal trade--United States--Costs.
Coal--Taxation--Poland.
Coal--Taxation--United States.
Princeton subject headings:
Coal mines and mining--Law and legislation--Compliance costs--Poland.
Coal mines and mining--Law and legislation--Compliance costs--United States.
Coal trade--Poland--Costs.
Coal trade--United States--Costs.
Coal--Taxation--Poland.
Coal--Taxation--United States.