Columbia subject headings:
Miners--Employment--Europe--History--Congresses.
Miners--Legal status, laws, etc.--Europe--History--Congresses.
Harvard subject headings:
Labor laws and legislation--Europe--History--Congresses.
Mineral industries--Europe--History--Congresses.
Miners--Legal status, laws, etc.--Europe--History--Congresses.
Princeton subject headings:
Miners--Employment--Europe--History--Congresses.