Columbia subject headings:
Costs, Industrial--United States--Statistics--Periodicals.
Pollution control equipment--United States--Costs--Statistics--Periodicals.
Pollution--Economic aspects--United States--Statistics--Periodicals.
Harvard subject headings:
Costs, Industrial--United States--Statistics--Periodicals.
Pollution control equipment--United States--Costs--Statistics--Periodicals.
Pollution--Economic aspects--United States--Statistics--Periodicals.
Princeton subject headings: