1. X-Ray investigations of colloid fractions of some American soils;Alexander,1938
2. Minerals present in soil colloids: II. Estimation in some representative soils;Alexander;Soil Sci.,1939
3. Concepts of soil and pedology;Arnold,1983
4. Land utilization in the United States: geographical aspects of the problem;Baker;Geogr. Rev.,1923
5. Soil classification. Soils and Men, U.S. Dept. Agric. yearbook for 1938;Baldwin,1938