Não informado. (1964). Soil and water. National Water and Soil Conservation Organization.
Chicago-referens (17:e uppl.)Não informado. Soil and Water. Wellington: National Water and Soil Conservation Organization, 1964.
MLA-referens (8:e uppl.)Não informado. Soil and Water. National Water and Soil Conservation Organization, 1964.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.