Columbia subject headings:
Agriculture and state--Canada.
Agriculture and state--United States.
Free trade--Canada.
Free trade--United States.
Tariff on farm produce--Canada.
Tariff on farm produce--United States.
Harvard subject headings:
Agriculture and state--Canada.
Agriculture and state--United States.
Free trade--Canada
Free trade--United States
Tariff on farm produce--Canada.
Tariff on farm produce--United States.
Princeton subject headings:
Agriculture and state--Canada.
Agriculture and state--United States.
Free trade--Canada.
Free trade--United States.
Tariff on farm produce--Canada.
Tariff on farm produce--United States.