Não informado. (2001). Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Zoological Society of Philadelphia.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Philadelphia, Pa: Zoological Society of Philadelphia, 2001.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Annual Report of the Board of Directors of the Zoological Society of Philadelphia. Zoological Society of Philadelphia, 2001.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.