Não informado. Extension Folder. North Carolina State College of Agriculture and Engineering, Agricultural Extension Service.
Chicago-referens (17:e uppl.)Não informado. Extension Folder. Raleigh, NC: North Carolina State College of Agriculture and Engineering, Agricultural Extension Service.
MLA-referens (8:e uppl.)Não informado. Extension Folder. North Carolina State College of Agriculture and Engineering, Agricultural Extension Service.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.