Willingham, W. F. (1983). Army engineers and the development of Oregon: A history of the Portland District, U.S. Army Corps of Engineers. U.S. Army Corps of Engineers.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रWillingham, William F. Army Engineers and the Development of Oregon: A History of the Portland District, U.S. Army Corps of Engineers. [Washington, D.C.?: U.S. Army Corps of Engineers, 1983.
एमएलए (8वां संस्करण) प्रशस्ति पत्रWillingham, William F. Army Engineers and the Development of Oregon: A History of the Portland District, U.S. Army Corps of Engineers. U.S. Army Corps of Engineers, 1983.
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