Não informado. (2012). Purdue Agricultures Magazine. Purdue University, College of Agriculture.
Chicago-referens (17:e uppl.)Não informado. Purdue Agricultures Magazine. West Lafayette, Ind: Purdue University, College of Agriculture, 2012.
MLA-referens (8:e uppl.)Não informado. Purdue Agricultures Magazine. Purdue University, College of Agriculture, 2012.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.