1. CHARLES H. ZIMMERMAN, Some Stability Problems of Vertically-Rising Aircraft, Paper presented to the West Coast Forum of the American Helicopter Society, Los Angeles, September 21–22, 1955.
2. Convertiplanes and Other VTOL Aircraft;WOODS,1956
3. CHARLES H. ZIMMERMAN, Some General Considerations Concerning VTOL Aircraft, Paper presented to SAE National Aeronautic Meeting, New York, April 9–12, 1956.
4. A Comparison Between Pay-Load Capabilities of VTOL and Conventional Aircraft;STEPNIEWSKI;Aero. Eng. Rev., Inst. Aero. Sci.,1956
5. J. P. CAMPBELL, Techniques for Testing Models of VTOL and STOL Airplanes, Presented to Wind Tunnel and Model Testing Panel of AGARD (Brussels, Belgium), August 27–31, 1956.