Não informado. (1949). Abstracts of recent published material on soil and water conservation. Agricultural Research Service, Soil and Water Conservation Division.
Chicago-referens (17:e uppl.)Não informado. Abstracts of Recent Published Material on Soil and Water Conservation. Washington: Agricultural Research Service, Soil and Water Conservation Division, 1949.
MLA-referens (8:e uppl.)Não informado. Abstracts of Recent Published Material on Soil and Water Conservation. Agricultural Research Service, Soil and Water Conservation Division, 1949.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.