1. Helicopter Blade Slap;Taylor,1964
2. B. W. McCormick 1965 Boeing Vertol Report (unpublished). A study of the vortex system of the Vertol 107 II Rotor.
3. I. A. Simons 1965 Private communication at the Institute of Sound and Vibration Research, Southampton University.
4. Helicopter Blade Slap;Leverton,1964
5. Sound generated aerodynamically (The Bakerian Lecture);Lighthill,1961