lower left in graphite: 20/30 Plowing; lower right in graphite: Clare Leighton
- Leighton, Clare. The Farmer's Year: A Calendar of English Husbandry. New York: Longmans, Green and Company, 1933, p. 48 (illustration for November).
- Fletcher, William D. Clare Leighton, An Exhibition: American Sheaves, English Seed Corn. Massachusetts: Boston Public Library, 1977, p. 13, no. 220.