Columbia subject headings:
Battistero di San Giovanni (Pisa, Italy)
Campo santo di Pisa.
Duomo (Pisa, Italy)
Leaning Tower (Pisa, Italy)
Harvard subject headings:
Battistero di San Giovanni (Pisa, Italy)
Campo santo di Pisa.
Duomo (Pisa, Italy)
Leaning Tower (Pisa, Italy)
Princeton subject headings: