A.M.S. (Series) ; L751. "AMS 4". Transverse Mercator projection. "Prepared by the Army Map Service (AMNS), Corps of Engineers, U.S. Army, Washington, D.C. Redrawn in 1950 from Korea 1:50,000, Japanese Imperial Land Survey, Hongch'ŏn, 1942.... Aerial photography Mar., Oct. 1947."
