Columbia subject headings:
Portugal--Foreign relations--19th century.
Portugal--Foreign relations--20th century.
Portugal--Politics and government.
Harvard subject headings:
Portugal--Foreign relations--19th century.
Portugal--Foreign relations--20th century.
Portugal--Politics and government--19th century.
Portugal--Politics and government--20th century.
Princeton subject headings:
Portugal--Foreign relations--19th century.
Portugal--Foreign relations--20th century.
Portugal--Politics and government--19th century.
Portugal--Politics and government--20th century.