Columbia subject headings:
Harvard subject headings:
Agriculture--Economic aspects--Periodicals
Agriculture--Economic aspects--United States--Periodicals
Natural resources--Periodicals
Natural resources--United States--Periodicals.
Princeton subject headings:
Agriculture--Economic aspects--Periodicals.
Agriculture--Economic aspects--United States--Periodicals.
Natural resources--Periodicals.
Natural resources--United States--Periodicals.
Periodicals.