Columbia subject headings:
Harvard subject headings:
Industries--Wales--Merthyr Tydfil--History.
Industries--Wales--Merthyr Tydfil.
Merthyr Tydfil (Wales)--Economic conditions.
Merthyr Tydfil (Wales)--History.
Merthyr Tydfil (Wales)--Social conditions.
Princeton subject headings:
Industries--Wales--Merthyr Tydfil--History.
Merthyr Tydfil (Wales)--History.
Merthyr Tydfil (Wales)--Social conditions.