Columbia subject headings:
Architecture, Medieval--Italy--Palermo.
Architecture, Norman--Italy--Palermo.
Palaces--Italy--Palermo.
Harvard subject headings:
Architecture, Norman--Italy--Palermo.
Palaces--Italy--Palermo.
Palermo (Italy)--Buildings, structures, etc.
Princeton subject headings:
Architecture, Norman--Italy--Palermo.
Palaces--Italy--Palermo.
Palermo (Italy)--Buildings, structures, etc.