Columbia subject headings:
Hydrology--Europe--History--Congresses.
Hydrology--Rome--Congresses.
Water-supply--Europe--History--Congresses.
Water-supply--Rome--Congresses.
Harvard subject headings:
Hydrology--Europe--History--Congresses.
Hydrology--Rome--Congresses.
Water-supply--Europe--History--Congresses.
Water-supply--Rome--Congresses.
Princeton subject headings:
Hydrology--Rome--Congresses.
Water-supply--Europe--History--Congresses.
Water-supply--Rome--Congresses.