Tractors and horses in the winter wheat belt, Oklahoma, Kansas, Nebraska.
By H. R. Tolley ... and W. R. Humphries.
- Washington, Govt. print off., 1924.
- 60 p. illus., map, diagrs. 23 cm.
- United States. Dept. of agriculture. Department bulletin no. 1202 .
Joint contribution from Bureau of public roads, Bureau of agricultural economics, Bureau of animal industry.