Columbia subject headings:
Friendship--Europe--History--Congresses.
Interpersonal relations and culture--Europe--History--Congresses.
Kinship--Europe--History--Congresses.
Harvard subject headings:
Friendship--History--To 1500--Congresses.
Social networks--History--To 1500--Congresses.
Princeton subject headings:
Friendship--History--To 1500--Congresses.
Social networks--History--To 1500--Congresses.