Williams, I. A., & Allen, J. E. (1991). Geologic history of the Columbia River Gorge, as interpreted from the historic Columbia River scenic highway (3rd ed., rev.). Oregon Historical Society Press.
Chicago Style (17th ed.) CitationWilliams, Ira A., and John Eliot Allen. Geologic History of the Columbia River Gorge, as Interpreted from the Historic Columbia River Scenic Highway. 3rd ed., rev. Portland, Or.: Oregon Historical Society Press, 1991.
MLA (8th ed.) CitationWilliams, Ira A., and John Eliot Allen. Geologic History of the Columbia River Gorge, as Interpreted from the Historic Columbia River Scenic Highway. 3rd ed., rev. Oregon Historical Society Press, 1991.
Warning: These citations may not always be 100% accurate.