Columbia subject headings:
Hotels--History--19th century--Congresses.
Hotels--History--20th century--Congresses.
Hotels--Italy--History--19th century--Congresses.
Hotels--Italy--History--20th century--Congresses.
Harvard subject headings:
Hotels--History--19th century--Congresses.
Hotels--History--20th century--Congresses.
Hotels--Italy--History--19th century--Congresses.
Hotels--Italy--History--20th century--Congresses.
Princeton subject headings:
Hotels--History--19th century--Congresses.
Hotels--History--20th century--Congresses.
Hotels--Italy--History--19th century--Congresses.
Hotels--Italy--History--20th century--Congresses.