1934, 1935, 1936, 1937, 1938, 1939, 1940, and 1941. Stanford Geospatial Center. This polygon shapefile is an index to 1:500,000 scale maps of South Korea and the Daitō Islands (Japan), titled '五十万分一興地圖 - Gojūmanbun no ichi Yōch... Stanford Digital Repository.