Não informado. (1887). Bulletin of the Pennsylvania Agricultural Experiment Station. Pennsylvania Agricultural Experiment Station.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Bulletin of the Pennsylvania Agricultural Experiment Station. Harrisburg, Pa: Pennsylvania Agricultural Experiment Station, 1887.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Bulletin of the Pennsylvania Agricultural Experiment Station. Pennsylvania Agricultural Experiment Station, 1887.
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