Cockrell, N., & Cockrell, B. (1978). Roofs over rivers: A guide to Oregon's covered bridges. Touchstone Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रCockrell, Nick, और Bill Cockrell. Roofs over Rivers: A Guide to Oregon's Covered Bridges. Beaverton, Ore.: Touchstone Press, 1978.
एमएलए (8वां संस्करण) प्रशस्ति पत्रCockrell, Nick, और Bill Cockrell. Roofs over Rivers: A Guide to Oregon's Covered Bridges. Touchstone Press, 1978.
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