Columbia subject headings:
Puerto Rico--History--1898-1952.
Puerto Rico--History--1952-1998.
Puerto Rico--Intellectual life--20th century.
Harvard subject headings:
Political culture--Puerto Rico--History--20th century.
Puerto Rico--History--20th century.
Puerto Rico--Politics and government--20th century.
Princeton subject headings:
Puerto Rico--History--1898-1952.
Puerto Rico--History--1952-1998.
Puerto Rico--Intellectual life--20th century.