Columbia subject headings:
Copper industry and trade--Chile--History.
Copper industry and trade--Employees--Labor unions--Chile--History.
Labor unions--Chile--History.
Sindicato Madeco (Chile)--History.
Harvard subject headings:
Princeton subject headings:
Copper industry and trade--Chile--History--20th century.
Labor unions--Chile--History--20th century.
Medina, Marcos.