Columbia subject headings:
Plebiscite--Puerto Rico.
Puerto Rico--Politics and government--1952-1998.
Harvard subject headings:
Plebiscite--Puerto Rico.
Puerto Rico--History
Puerto Rico--History--Autonomy and independence movements.
Puerto Rico--Relations--United States.
Referendum--Puerto Rico.
United States--Relations--Puerto Rico.
Princeton subject headings:
Plebiscite--Puerto Rico.
Puerto Rico--Politics and government--1952-1998.