Columbia subject headings:
Harvard subject headings:
Germany--Civilization--Foreign influences--Congresses.
Germany--Relations--Portugal--Congresses.
Portugal--Civilization--Foreign influences--Congresses.
Portugal--Relations--Germany--Congresses.
Princeton subject headings:
Germans--Portugal--Congresses.
Germany--Relations--Portugal--Congresses.
Portugal--Relations--Germany--Congresses.
Portuguese--Germany--Congresses.