Columbia subject headings:
Feudalism--Germany--Congresses.
Feudalism--Italy--Congresses.
Harvard subject headings:
Feudalism--Germany--Congresses.
Feudalism--Germany--History--12th century--Congresses.
Feudalism--Germany--History--13th century--Congresses.
Feudalism--Italy--Congresses.
Feudalism--Italy--History--12th century--Congresses.
Feudalism--Italy--History--13th century--Congresses.
Holy Roman Empire--History--Congresses.
Princeton subject headings:
Feudalism--Germany--History--12th century--Congresses.
Feudalism--Germany--History--13th century--Congresses.
Feudalism--Italy--History--12th century--Congresses.
Feudalism--Italy--History--13th century--Congresses.
Holy Roman Empire--History--Congresses.