Columbia subject headings:
Portugal--History--19th century.
Portugal--History--20th century.
Portugal--History--21st century.
Harvard subject headings:
History in art
Portugal--History--19th century.
Portugal--History--20th century.
Portugal--History--21st century.
Portugal--Social life and customs.
Princeton subject headings:
Portugal--History--19th century.
Portugal--History--20th century.
Portugal--History--21st century.