Não informado. (2001). Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Zoological Society of Philadelphia.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Philadelphia, Pa: Zoological Society of Philadelphia, 2001.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Zoological Society of Philadelphia, 2001.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.