Columbia subject headings:
Friendship--History--To 1500--Congresses.
Harvard subject headings:
Civilization, Medieval--Congresses
Friendship in literature--History--To 1500--Congresses.
Friendship--Europe--History--To 1500--Congresses.
Princeton subject headings:
Civilization, Medieval--Congresses.
Friendship in literature--History--To 1500--Congresses.
Friendship--Europe--History--To 1500--Congresses.