Columbia subject headings:
Harvard subject headings:
Water--Pollution--Merrimack River Watershed (N.H. and Mass.)--Congresses.
Water--Pollution--Nashua River watershed (Mass. and N.H.)--Congresses.
Princeton subject headings:
Water--Pollution--Merrimack River Watershed (N.H. and Mass.)--Congresses.
Water--Pollution--Nashua River Watershed (Mass. and N.H.)--Congresses.