1921. Geological Survey (U.S.). Contour interval 20 feet.;"Surveyed in 1914, 1916 and 1920.";"Surveyed in cooperation with the States of Kentucky and Illinois."; (W 88⁰30ʹ00ʺ--W 8... Geological Survey (U.S.), Geological Survey Division (Urbana, Ill.), and Kentucky Geological Survey (Lexington, Ky.).
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1929. Geological Survey (U.S.). Contour interval 20 feet.;"Culture and drainage in part compiled from aerial photographs taken by Air Corps, U.S. Army";"Surveyed in 1926";Relief s... Geological Survey (U.S.), Geological Survey Division (Urbana, Ill.), and Kentucky Geological Survey (Lexington, Ky.).
1929. Geological Survey (U.S.). Contour interval 20 feet.;"Illinos culture and drainage in part compiled from aerial photographs taken by Air Corps, U.S. Army";"Surveyed in 1926";... Geological Survey (U.S.), Geological Survey Division (Urbana, Ill.), and Kentucky Geological Survey (Lexington, Ky.).
1960. Geological Survey (U.S.). Contour interval 20 feet.;"Topography from aerial photographs by photogrammetric methods and by planetable surveys. Aerial photographs taken 1957";... Geological Survey (U.S.), Geological Survey Division (Urbana, Ill.), and Kentucky Geological Survey (Lexington, Ky.).