Columbia subject headings:
Harvard subject headings:
Architecture, Medieval--Europe--Congresses.
Cathedrals--Europe--History--Congresses.
Church decoration and ornament--Europe--Congresses.
Duomo di Orvieto (Orvieto, Italy)--Congresses.
Sculpture, Italian--Italy--Orvieto--Congresses.
Sculpture, Medieval--Europe--Congresses.
Princeton subject headings:
Architecture, Medieval--Europe--Congresses.
Cathedrals--Europe--History--Congresses.