Columbia subject headings:
Agricultural chemicals--United States--Statistics--Periodicals.
Fertilizers--United States--Statistics--Periodicals.
Field crops--United States--Statistics--Periodicals.
Pesticides--United States--Statistics--Periodicals.
Harvard subject headings:
Agricultural chemicals--United States--Statistics--Periodicals.
Fertilizers--United States--Statistics--Periodicals.
Field crops--United States--Statistics--Periodicals.
Pesticides--United States--Statistics--Periodicals.
Princeton subject headings: