Jenkins, O. P. (1924). Geological investigation of the coal fields of Skagit county, Washington. F.M. Lamborn, public printer.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रJenkins, Olaf P. Geological Investigation of the Coal Fields of Skagit County, Washington. Olympia: F.M. Lamborn, public printer, 1924.
एमएलए (8वां संस्करण) प्रशस्ति पत्रJenkins, Olaf P. Geological Investigation of the Coal Fields of Skagit County, Washington. F.M. Lamborn, public printer, 1924.
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