Columbia subject headings:
Harvard subject headings:
Monarchy--England--History--19th century--Congresses.
Monarchy--England--History--20th century--Congresses.
Monarchy--Europe--History--Congresses.
Monarchy--Germany--History--19th century--Congresses.
Monarchy--Germany--History--20th century--Congresses.
Princeton subject headings:
Monarchy--Europe--History--19th century--Congresses.
Monarchy--Europe--History--20th century--Congresses.