Columbia subject headings:
Canada. Treaties, etc.
Duty-free importation--Law and legislation--Canada.
Duty-free importation--Law and legislation--United States.
Tariff--Law and legislation--Canada.
Tariff--Law and legislation--United States.
Harvard subject headings:
Canada. Treaties, etc. 1988 January 2.
Duty-free importation--Law and legislation--Canada.
Duty-free importation--Law and legislation--United States.
Tariff--Law and legislation--Canada.
Tariff--Law and legislation--United States.
Princeton subject headings: