Não informado. (2018). Research Circular. Pennsylvania Department of Forests and Waters.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Research Circular. Harrisburg, Pa: Pennsylvania Department of Forests and Waters, 2018.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Research Circular. Pennsylvania Department of Forests and Waters, 2018.
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