Columbia subject headings:
Harvard subject headings:
Bologna (Italy)--Buildings, structures, etc.
Canals--Italy--Bologna--History.
Inland navigation--Italy--Bologna--History.
Water-supply--Italy--Bologna--History.
Princeton subject headings:
Bologna (Italy)--Buildings, structures, etc.
Canals--Italy--Bologna--History.
Inland navigation--Italy--Bologna--History.
Water-supply--Italy--Bologna--History.