1. Productivity ratings in the soil survey report;Ableiter,1937
2. Productivity ratings of soil types;Ableiter,1940
3. Soil productivity ratings;Ableiter,1950
4. A proposed method for classifying and evaluating soils on the basis of productivity and use suitabilities;Anderson;Nebr. Agric. Exp. Stn. Res. Bull.,1938
5. A classification of natural land-types according to productivity, based on the soil survey;Barnes;Am. Soil Surv. Assoc. Bull.,1935