Columbia subject headings:
Architecture--Italy--Congresses.
Building stones--Italy--Congresses.
Stone buildings--Italy--Congresses.
Harvard subject headings:
Building stones--Italy--Congresses.
Stone buildings--Conservation and restoration--Italy--Congresses.
Stone buildings--Italy--Congresses.
Princeton subject headings:
Architecture--Italy--Congresses.
Building stones--Italy--Congresses.
Stone buildings--Italy--Congresses.