U.S. Air Force. Office of Air Force History. Case Studies in the Development of Close Air Support . Edited by Benjamin Franklin Cooling. Developments to 1939, by Lee Kennett, pp 13-70.
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The U.S. Air Service in World War I . Compiled and edited by Dr. Maurer Maurer. Maxwell AFB, AL, Albert F. Simpson Historical Research Center, 1978-1979. The Final Report and a Tactical History. Early Concepts of Military Aviation.