Columbia subject headings:
Sewage--Purification--Periodicals.
Water quality management--Periodicals.
Water--Pollution--Periodicals.
Harvard subject headings:
Sewage--Purification--Periodicals
Water quality management--Periodicals
Water--Pollution--Periodicals
Princeton subject headings:
Periodicals.
Sewage--Purification--Periodicals.
Water quality management--Periodicals.
Water--Pollution--Periodicals.