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