Soil Survey Staff, 1999. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys (2nd ed.). US Department of Agriculture Soil Conservation Service, Washington DC. Digitale versie:USDA Soil Taxonomy. Gearchiveerd op 22 november 2013.
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Soil Survey Staff, 1999. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys (2nd ed.). US Department of Agriculture Soil Conservation Service, Washington DC. Digitale versie:USDA Soil Taxonomy. Gearchiveerd op 22 november 2013.