Allen, J. (1924). State of Washington showing state highways and principal county roads. Shell Oil Company of California.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रAllen, James. State of Washington Showing State Highways and Principal County Roads. California: Shell Oil Company of California, 1924.
एमएलए (8वां संस्करण) प्रशस्ति पत्रAllen, James. State of Washington Showing State Highways and Principal County Roads. Shell Oil Company of California, 1924.
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