http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Usual planting and harvesting dates for U.S. field crops
"Supersedes Agriculture Handbook Number 283, Usual planting and harvesting dates, by states, in principal producing areas, revised August 1972"--P. i.
Agriculture handbook (United States. Department of Agriculture) ; no. 628