Washington State Historical Society—The Treaty Trail: U.S.-Indian Treaty Councils in the Northwest Gustav Sohon: Indian Pictorialist, Interpreter, and Topographical Assistant - 1825-1903 University of Idaho entry
Washington State Historical Society — The Treaty Trail: U.S.-Indian Treaty Councils in the Northwest Gustav Sohon: Indian Pictorialist, Interpreter, and Topographical Assistant — 1825—1903  (англ.)