Columbia subject headings:
Europe--Economic conditions.
Precious metals--America--History.
Precious metals--Europe--History.
Precious metals--Portugal--History.
Precious metals--Spain--History.
Harvard subject headings:
Europe--Economic conditions.
Precious metals--America--History.
Precious metals--Europe--History.
Precious metals--Portugal--History.
Precious metals--Spain--History.
Princeton subject headings:
Europe--Economic conditions.
Precious metals--America--History.
Precious metals--Europe--History.
Precious metals--Portugal--History.
Precious metals--Spain--History.