Olmstead, Alan L. (June 1975). "The Mechanization of Reaping and Mowing in American Agriculture". The Journal of Economic History. 35 (2): 327. doi:10.1017/s0022050700075082. S2CID154366322.
Olmstead, Alan L. (June 1975). "The Mechanization of Reaping and Mowing in American Agriculture". The Journal of Economic History. 35 (2): 327. doi:10.1017/s0022050700075082. S2CID154366322.