1. Advancing blade concept (ABC) development test program;Ruddell,1981
2. Ruddell, A. J. (1981). Advancing blade concept (ABC) technology demonstrator. NASA-ADA-100181.
3. Harrington, D. (1951). Full-scale-tunnel investigation of the static-thrust performance of a coaxial helicopter rotor. NACA-TN-2318.
4. Landgrebe, A. J., Bellinger, E. D. (1974). Experimental investigation of model variable-geometry and ogee tip rotors. NASA-CR-2275.