Columbia subject headings:
Architecture, Gothic--Italy--Orvieto--Congresses.
Cathedrals--Italy--Congresses.
Church decoration and ornament--Italy--Orvieto--Congresses.
Duomo di Orvieto (Orvieto, Italy)--Congresses.
Orvieto (Italy)--Buildings, structures, etc.--Congresses.
Harvard subject headings:
Architecture, Gothic--Italy--Orvieto--Congresses.
Church decoration and ornament--Italy--Orvieto--Congresses.
Duomo di Orvieto--Congresses.
Orvieto (Italy)--Buildings, structures, etc.--Congresses.
Princeton subject headings:
Architecture, Gothic--Italy--Congresses.
Church architecture--Italy--Congresses.
Duomo di Orvieto (Orvieto, Italy)--Congresses.
Orvieto (Italy)--Buildings, structures, etc.--Congresses.