1980. United States. Soil Conservation Service. Base source: USGS 1:100,000 county base map dated 1978; interpretations derived from soil map constructed 1972.; "Projection and 10,000-metre grid ... Dept. of Agriculture, Soil Conservation Service (Washington.).
    
  
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      1980. United States. Soil Conservation Service. Base source: USGS 1:100,000 county base dated 1979; interpretations derived from soil map constructed 1979.; "Projection and 10,000-metre grid tick... Dept. of Agriculture, Soil Conservation Service (Washington.).
    
  
    
      1980. United States. Soil Conservation Service. Base source: USGS 1:100,000 county base dated 1978; interpretations derived from soil map constructed 1956.; "Projection and 10,000-metre grid tick... Dept. of Agriculture, Soil Conservation Service (Washington.).