Columbia subject headings:
Foreign trade regulation--North America.
Free trade--Canada.
Free trade--Mexico.
Free trade--North America.
Free trade--United States.
North American Free Trade Agreement
Tariff--Law and legislation--North America.
Harvard subject headings:
Foreign trade regulation--North America.
Free trade--Canada
Free trade--Mexico
Free trade--North America
Free trade--United States
North American Free Trade Agreement
Tariff--Law and legislation--North America.
Princeton subject headings:
Foreign trade regulation--North America.
Free trade--North America.
North American Free Trade Agreement
Tariff--Law and legislation--North America.