Butler, K. (2013). Knocking on heaven's door: The path to a better way of death (First Scribner hardcover edition.). Scribner.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रButler, Katy. Knocking on Heaven's Door: The Path to a Better Way of Death. First Scribner hardcover edition. New York, NY: Scribner, 2013.
एमएलए (8वां संस्करण) प्रशस्ति पत्रButler, Katy. Knocking on Heaven's Door: The Path to a Better Way of Death. First Scribner hardcover edition. Scribner, 2013.
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