Allen, J. E. (1979). The magnificent gateway: A layman's guide to the geology of the Columbia River Gorge. Timber Press.
Cita Chicago Style (17a ed.)Allen, John Eliot. The Magnificent Gateway: A Layman's Guide to the Geology of the Columbia River Gorge. Forest Grove, Or.: Timber Press, 1979.
Cita MLA (8a ed.)Allen, John Eliot. The Magnificent Gateway: A Layman's Guide to the Geology of the Columbia River Gorge. Timber Press, 1979.
Precaución: Estas citas no son 100% exactas.