Não informado. (1980). Soil and water conservation news. U.S. Department of Agriculture, Soil Conservation Service.
Citação do estilo Chicago (17ª ed.)Não informado. Soil and Water Conservation News. Washington: U.S. Department of Agriculture, Soil Conservation Service, 1980.
Citação MLA (8ª ed.)Não informado. Soil and Water Conservation News. U.S. Department of Agriculture, Soil Conservation Service, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.