Não informado. Extension bulletin. Purdue University, Department of Agricultural Extension.
Chicago-referens (17:e uppl.)Não informado. Extension Bulletin. Lafayette, Ind: Purdue University, Department of Agricultural Extension.
MLA-referens (8:e uppl.)Não informado. Extension Bulletin. Purdue University, Department of Agricultural Extension.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.