Columbia subject headings:
Field crops--United States--Statistics.
Harvesting time--United States--Statistics.
Planting time--United States--Statistics.
Harvard subject headings:
Field crops--United States--Statistics.
Harvesting time--United States--Statistics.
Planting time--United States--Statistics.
Princeton subject headings:
Field crops--United States--Statistics.
Harvesting time--United States--Statistics.
Planting time--United States--Statistics.
Statistics.