Não informado. (1887). Bulletin of the Pennsylvania Agricultural Experiment Station. Pennsylvania Agricultural Experiment Station.
Chicago-referens (17:e uppl.)Não informado. Bulletin of the Pennsylvania Agricultural Experiment Station. Harrisburg, Pa: Pennsylvania Agricultural Experiment Station, 1887.
MLA-referens (8:e uppl.)Não informado. Bulletin of the Pennsylvania Agricultural Experiment Station. Pennsylvania Agricultural Experiment Station, 1887.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.