Columbia subject headings:
Pisa (Italy)--Buildings, structures, etc.
Towers--Italy--Pisa.
Harvard subject headings:
Pisa (Italy)--Buildings, structures, etc.
Pisa (Italy)--Pictorial works.
Towers--Italy--Pisa.
Princeton subject headings:
Pisa (Italy)--Buildings, structures, etc.
Towers--Italy--Pisa.