Columbia subject headings:
Harvard subject headings:
Free trade--Canada
Free trade--Canada--Congresses
Free trade--Mexico
Free trade--Mexico--Congresses.
Free trade--United States
Free trade--United States--Congresses
Industries--Mexican-American Border Region--Congresses.
Industries--Mexican-American Border Region.
Mexican-American Border Region--Economic conditions--Congresses.
Mexican-American Border Region--Economic conditions.
Mexico, North--Economic conditions--Congresses.
Mexico, North--Economic conditions.
Princeton subject headings:
Free trade--Canada.
Free trade--Mexico.
Free trade--United States.
Industries--Mexican-American Border Region.
Mexican-American Border Region--Economic conditions.
Mexico, North--Economic conditions.