Columbia subject headings:
Harvard subject headings:
Cathedrals--Europe--Congresses.
Cathedrals--Italy--Palermo.
Cattedrale di Palermo--Congresses.
Cattedrale di Palermo.
Church architecture--Italy--Palermo.
Palermo (Italy)--Buildings, structures, etc.
Palermo (Italy)--Buildings, structures, etc.--Congresses.
Religion and culture--Italy--Palermo--Congresses.
Princeton subject headings:
Cattedrale di Palermo--Congresses.
Palermo (Italy)--Buildings, structures, etc.--Congresses.