Columbia subject headings:
Harvard subject headings:
Monarchy--Portugal--History--Congresses.
Monarchy--Spain--History--Congresses.
Portugal--Relations--Spain--Congresses.
Spain--Relations--Portugal--Congresses.
Princeton subject headings:
Monarchy--Portugal--History--16th century--Congresses.
Monarchy--Portugal--History--17th century--Congresses.
Portugal--History--Spanish dynasty, 1580-1640--Congresses.