Columbia subject headings:
Basilica di San Petronio (Bologna, Italy)--Organs.
Organ (Musical instrument)--History--Sources.
Organ (Musical instrument)--Italy--Bologna.
Harvard subject headings:
Basilica di San Petronio (Bologna, Italy)--Organs.
Organ (Musical instrument)--History--Sources.
Organ (Musical instrument)--Italy--Bologna.
Princeton subject headings:
Basilica di San Petronio (Bologna, Italy)--Organs.
Organ (Musical instrument)--History--Sources.
Organ (Musical instrument)--Italy--Bologna.