Columbia subject headings:
Harvard subject headings:
Coal miners--Wales, South--History.
Coal trade--Wales, South--History.
Labor movement--Wales, South--History.
Wales, South--Economic conditions.
Wales, South--Social conditions.
Princeton subject headings:
Coal miners--Wales, South--History--19th century.
Coal miners--Wales, South--History--20th century.
Wales, South--History--19th century.
Wales, South--History--20th century.
Wales, South--Social conditions--19th century.
Wales, South--Social conditions--20th century.