Columbia subject headings:
Coal mines and mining--United States--Statistics--Periodicals.
Coal trade--United States--Statistics--Periodicals.
Coal--Statistics--Periodicals.
Harvard subject headings:
Coal mines and mining--United States--Statistics--Periodicals.
Coal trade--United States--Statistics--Periodicals.
Coal--Statistics--Periodicals.
Princeton subject headings:
Coal mines and mining--United States--Statistics--Periodicals.
Coal trade--United States--Statistics--Periodicals.
Coal--Statistics--Periodicals.
Periodicals.
Statistics.