7 2011 97 43 2011 98 41 | |
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3 2011 64 110 2011 65 107 | Committee on 21st Century Systems Agriculture 2010 |
Principles of Soil Conservation and Management.
30United States Department of Agriculture, Alternative Farming Systems Information Center | Paul Weiss chairman of renewable resources study 1962 |
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39 2011 112 26 2011 113 25 | 2 2011 68 104 2011 69 100 2011 70 96 |
5 2011 140 8 2011 141 7.
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