Columbia subject headings:
Puerto Rico--Foreign relations--United States.
Puerto Rico--Politics and government.
United States--Foreign relations--Puerto Rico.
Harvard subject headings:
Puerto Rico--Foreign relations--United States.
Puerto Rico--Politics and government.
United States--Foreign relations--Puerto Rico.
Princeton subject headings:
Puerto Rico--Economic conditions.
Puerto Rico--Politics and government.
Puerto Rico--Relations--United States.
United States--Relations--Puerto Rico.