Columbia subject headings:
El Chamizal (Mexico and Tex.)
Mexico--Boundaries--United States.
United States--Boundaries--Mexico.
Harvard subject headings:
El Chamizal (Mexico and Tex.)
Mexico--Boundaries--United States.
United States--Boundaries--Mexico.
Princeton subject headings:
El Chamizal (Mexico and Tex.)
Mexico--Boundaries--United States.
United States--Boundaries--Mexico.