Não informado. AERR. University of Illinois at Urbana-Champaign, Agricultural Experiment Station.
Chicago-referens (17:e uppl.)Não informado. AERR. Urbana, Ill: University of Illinois at Urbana-Champaign, Agricultural Experiment Station.
MLA-referens (8:e uppl.)Não informado. AERR. University of Illinois at Urbana-Champaign, Agricultural Experiment Station.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.