Johnson, Albert G.White, Donald B.Smithberg, Margaret H.2020-03-022020-03-021966https://hdl.handle.net/11299/211872Investigation No. 615 In Cooperation with U. S. Department of Commerce, Bureau of Public Roads, Minnesota Highway Department, Minnesota Local Road Research Board Miscellaneous Journal Series Article 1259, Agricultural Experiment Station, University of MinnesotaenReport