Williams. Endangered and Disappearing Birds of the Midwest. Indiana University Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रWilliams. Endangered and Disappearing Birds of the Midwest. Indiana University Press.
एमएलए (9वां संस्करण) प्रशस्ति पत्रWilliams. Endangered and Disappearing Birds of the Midwest. Indiana University Press.
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