1. Barman, Th. von and Burgers, J. M., Durand's Aerodynamic Theory, Vol.2, Div. E,J. Springer, Berlin,1934, pp.218-220and 326-329.
2. 2Kerber, L. V., Durand's Aerodynamic Theory, Vol.5, Div. O,J. Springer, Berlin,1934, pp.333-337.
3. Trimmed drag considerations