Não informado. (1971). Environmental data service. Environmental Data Service.
Chicago-referens (17:e uppl.)Não informado. Environmental Data Service. Rockville, Md: Environmental Data Service, 1971.
MLA-referens (8:e uppl.)Não informado. Environmental Data Service. Environmental Data Service, 1971.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.