Columbia subject headings:
Harvard subject headings:
Sandhogs--Switzerland--Social conditions.
Sandhogs--Switzerland.
Tunneling--Switzerland--History.
Underground construction Switzerland.
Underground construction.
Women--Switzerland--Social conditions
Princeton subject headings:
Sandhogs--Switzerland--Social conditions.
Sandhogs--Switzerland.
Tunneling--Switzerland--History.
Underground construction--Switzerland.
Women--Switzerland--Social conditions.