Allen, J. E. (1979). The magnificent gateway: A layman's guide to the geology of the Columbia River Gorge. Timber Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रAllen, John Eliot. The Magnificent Gateway: A Layman's Guide to the Geology of the Columbia River Gorge. Forest Grove, Or.: Timber Press, 1979.
एमएलए (8वां संस्करण) प्रशस्ति पत्रAllen, John Eliot. The Magnificent Gateway: A Layman's Guide to the Geology of the Columbia River Gorge. Timber Press, 1979.
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