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2. Land Evaluation for Agricultural Land use Planning. An Ecological Approach;Beek,1971
3. Aerial Photo-interpretation for Soil Surveys;Bennema;Lecture notes ITC courses Photo-interpretation in Soil Surveying,1969
4. Benson, L.A., Frazee, C.J. and Waltz, F.A., 1973. Analysis of Remotely Sensed Data for Detecting Soil Limitations. South Dakota Agr. Exp. Station. Journal Series No 1168. SDSU-RSI-J-73–05: 9 pp
5. Bergsma, E., 1974. Soil Erosion Sequences on Aerial Photographs. ITC Journal 1974/3, Enschede, The Netherlands: pp. 342–376