PBS Distribution (Firm), Morgan, C., Moss, C., Colbeck, M., & Birkhead, M. (2010). Echo: An elephant to remember. PBS Distribution.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रPBS Distribution (Firm), Chris Morgan, Cynthia Moss, Martyn Colbeck, और Mike Birkhead. Echo: An Elephant to Remember. [United States]: PBS Distribution, 2010.
एमएलए (8वां संस्करण) प्रशस्ति पत्रPBS Distribution (Firm), et al. Echo: An Elephant to Remember. PBS Distribution, 2010.
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