Columbia subject headings:
Harvard subject headings:
Water--History--Congresses.
Water-supply--Elbe River Valley (Czech Republic and Germany)--Management--History--Congresses.
Water-supply--Elbe River Valley (Czech Republic and Germany)--Management.
Water-supply--Germany--Hamburg--Management--History--Congresses.
Water-supply--Germany--Hamburg--Management.
Water-supply--Management
Water-supply--Management--History--Congresses.
Princeton subject headings:
Water-supply--Elbe River Valley (Czech Republic and Germany)--Management--Congresses.
Water-supply--Germany--Hamburg--Management--Congresses.
Water-supply--Management--Congresses.