Columbia subject headings:
Merthyr Tydfil (Wales)--History.
Harvard subject headings:
Iron industry and trade--Wales--Merthyr Tydfil--History.
Merthyr Tydfil (Wales)--History.
Princeton subject headings:
Iron industry and trade--Wales--Merthyr Tydfil--History.
Merthyr Tydfil (Wales)--History.
Merthyr Tydfil (Wales)--Politics and government.
Merthyr Tydfil (Wales)--Social conditions.