Columbia subject headings:
Architecture, Medieval--Conservation and restoration--Italy--Palermo--Congresses.
Cathedrals--Conservation and restoration--Italy--Palermo--Congresses.
Cattedrale di Palermo--Congresses.
Palermo (Italy)--Buildings, structures, etc.--Congresses.
Harvard subject headings:
Princeton subject headings:
Architecture, Medieval--Italy--Palermo--Congresses.
Cathedrale di Palermo--Congresses.
Church architecture--Italy--Palermo--Congresses.