Não informado. (1935). Soil conservation. U.S. Department of Agriculture, Soil Conservation Service.
Chicago-Zitierstil (17. Ausg.)Não informado. Soil Conservation. Washington: U.S. Department of Agriculture, Soil Conservation Service, 1935.
MLA-Zitierstil (8. Ausg.)Não informado. Soil Conservation. U.S. Department of Agriculture, Soil Conservation Service, 1935.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.