Columbia subject headings:
Land tenure--Law and legislation--Mexico.
Mexico--Foreign relations--United States.
Petroleum--Mexico.
United States--Foreign relations--Mexico.
Harvard subject headings:
Land tenure--Law and legislation--Mexico
Land tenure--Mexico--Law.
Mexico--Foreign relations--United States.
Petroleum--Mexico
United States--Foreign relations--Mexico.
Princeton subject headings:
Land tenure--Law and legislation--Mexico.
Mexico--Foreign relations--United States.
Petroleum--Mexico.
United States--Foreign relations--Mexico.