1. M. Tobak, NACA-TR-1188 (August 1954).
2. A unified unsteady lifting-line theory
3. J.G. Leishman, Principles of Helicopter Aerodynamics (Cambridge, New York, 2006), pp. 423–480.
4. R.T. Jones, NACA-TN-682 (January 1939).
5. B.H. Gothert, NACA-TM-1105 (October 1946).