Columbia subject headings:
Harvard subject headings:
Agriculture and state--United States.
Soil conservation--Economic aspects--United States.
Soil conservation--Government policy--United States
Soil erosion--Economic aspects--United States.
Soil erosion--United States
Princeton subject headings:
Agriculture and state--United States.
Soil conservation--Economic aspects--United States.
Soil conservation--Government policy--United States.
Soil erosion--Economic aspects--United States.
Soil erosion--United States.