Columbia subject headings:
Coal miners--Wales, North.
Coal mines and mining--Wales, North--History--20th century.
National Union of Mineworkers.
Wales, North--Economic conditions--20th century.
Wales, North--Politics and government--20th century.
Wales, North--Social conditions--20th century.
Harvard subject headings:
Coal miners--Wales, North--History--20th century.
Coal mines and mining--Wales, North--History--20th century.
Wales, North--Economic conditions.
Wales, North--History--20th century.
Wales, North--Politics and government--20th century.
Wales, North--Social conditions.
Princeton subject headings:
Coal miners--Wales, North.
Coal mines and mining--Wales, North--History--20th century.
National Union of Mineworkers.
Wales, North--Economic conditions--20th century.
Wales, North--Politics and government--20th century.
Wales, North--Social conditions--20th century.