Columbia subject headings:
Harvard subject headings:
Plebiscite--Puerto Rico.
Puerto Rico--Foreign relations--United States.
Puerto Rico--Politics and government--1952-
Puerto Rico--Politics and government--1952-1998.
United States--Foreign relations--Puerto Rico.
Princeton subject headings:
Plebiscite--Puerto Rico.
Puerto Rico--Foreign relations--United States.
Puerto Rico--Politics and government--1998-
United States--Foreign relations--Puerto Rico.