@article{Pond:106073,
      author = {Pond, George A. and Schwantes, Arthur J.},
      title = {{Tractor Costs and Rates of Performance: A Preliminary  Report of Data Secured in 1941 Covering the Cost of  Operation and the Rate of Performance on Farm Tractors in  Minnesota and a Summary for the 3-Year Period, 1939-1941}},
      series = {Mimeographed Report},
      pages = {12},
      year = {1942},
}