Sprague, M. (1964). The great gates: The story of the Rocky Mountain passes ([1st ed.].). Little, Brown.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रSprague, Marshall. The Great Gates: The Story of the Rocky Mountain Passes. [1st ed.]. Boston: Little, Brown, 1964.
एमएलए (8वां संस्करण) प्रशस्ति पत्रSprague, Marshall. The Great Gates: The Story of the Rocky Mountain Passes. [1st ed.]. Little, Brown, 1964.
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