Columbia subject headings:
Architecture--Conservation and restoration--Italy--Pisa.
Leaning Tower (Pisa, Italy)
Towers--Conservation and restoration--Italy--Pisa.
Harvard subject headings:
Duomo (Pisa, Italy)
Towers--Italy
Princeton subject headings:
Architecture--Conservation and restoration--Italy--Pisa.
Leaning Tower (Pisa, Italy)
Towers--Conservation and restoration--Italy--Pisa.