Columbia subject headings:
Coal trade--Canada--Statistics--Periodicals.
Coal trade--Europe--Statistics--Periodicals.
Coal trade--North America--Statistics--Periodicals.
Coal trade--United States--Statistics--Periodicals.
Harvard subject headings:
Coal trade--Canada--Statistics--Periodicals.
Coal trade--Europe--Statistics--Periodicals.
Coal trade--North America--Statistics--Periodicals.
Coal trade--United States--Statistics--Periodicals.
Princeton subject headings:
Coal trade--Europe--Statistics--Periodicals.
Coal trade--North America--Statistics--Periodicals.