Columbia subject headings:
Mining engineering--Italy--Valganna--History.
Tunnels--Italy--Valganna.
Underground construction.
Valganna (Italy)--History.
Harvard subject headings:
Mining engineering--Italy--Valganna--History.
Tunnels--Italy--Valganna.
Underground construction
Valganna (Italy)--History.
Princeton subject headings:
Mining engineering--Italy--Valganna--History.
Tunnels--Italy--Valganna.
Underground construction.
Valganna (Italy)--History.