Columbia subject headings:
Mexico--Foreign relations--United States.
Petroleum industry and trade--Mexico.
United States--Foreign relations--Mexico.
Harvard subject headings:
Mexico--Dependency on United States.
Mexico--Foreign economic relations--United States.
Mexico--Foreign relations--United States.
Petroleum industry and trade--Government ownership--Mexico
Petroleum industry and trade--Mexico
United States--Foreign economic relations--Mexico.
United States--Foreign relations--Mexico.
Princeton subject headings:
Mexico--Foreign relations--United States.
Petroleum industry and trade--Mexico.
United States--Foreign relations--Mexico.