Columbia subject headings:
Harvard subject headings:
Free trade--Mexico--Sonora (State)--Congresses.
Sonora (Mexico : State)--Economic conditions--Congresses.
Princeton subject headings:
Canada--Commercial policy--Congresses.
Free trade--Canada--Congresses.
Free trade--Mexico--Congresses.
Free trade--United States--Congresses.
Mexico--Commercial policy--Congresses.
Sonora (Mexico : State)--Commerce.--Congresses.
United States--Commercial policy--Congresses.