Steel plow
Steel Plow
"CHAPTER 1: New Implements Revolutionize Farming." Everyday Life: Inventions. 6-13. US: Social Studies School Service, 1999. History Reference Center. Web. 1 Oct. 2014.
Frazier, Ian. "John Deere Plow." Smithsonian 41.7 (2013): 72-114. History Reference Center. Web. 30 Sept. 2014.