Columbia subject headings:
Drinking water--Congresses.
Sanitation--Congresses.
Sewage disposal--Congresses.
Water-supply--Congresses.
Harvard subject headings:
Drinking water--Congresses.
Sanitation--Congresses.
Sewage disposal--Congresses
Water-supply--Congresses
Princeton subject headings:
Drinking water--Congresses.
Sanitation--Congresses.
Sewage disposal--Congresses.
Water-supply--Congresses.