Columbia subject headings:
Harvard subject headings:
Environmental sciences--Congresses
Human ecology--History--Congresses.
Water use--Germany--History--Congresses.
Water use--History--Congresses.
Water--History--Congresses.
Water-supply--Germany--Management--Congresses.
Water-supply--Management--Congresses
Water-supply--Political aspects--Congresses.
Princeton subject headings:
Environmental sciences--Congresses.
Human ecology--History--Congresses.
Water use--Germany--History--Congresses.
Water use--History--Congresses.
Water--History--Congresses.
Water-supply--Germany--Management--Congresses.
Water-supply--Management--Congresses.
Water-supply--Political aspects--Congresses.