Columbia subject headings:
Canada--Commerce--United States.
Free trade.
Tariff--Canada.
Tariff--United States.
United States--Commerce--Canada.
Harvard subject headings:
Canada--Commerce--United States.
Free trade.
Tariff--Canada
Tariff--United States.
United States--Commerce--Canada.
Princeton subject headings:
Canada--Commerce--United States.
Free trade--Canada.
Free trade--United States.
Tariff--Canada.
Tariff--United States.
United States--Commerce--Canada.