1. Differential equations of motion for combined flapwise bending, chordwise bending and torsion of twisted nonuniform rotor blades;Houbolt;National Advisory Committee for Aeronautics Report 1346,1958
2. Natural frequencies in coupled bending and torsion of twisted rotating and nonrotating blades;Isakson;NASA CR-65 NSG 27–59,1964
3. Coupled bending and torsional vibrations in a twisted, rotating blade;Montoya;The Brown Boveri Review,1966
4. Equations of motion of rotating pretwisted blades in bending-bending-torsion with effects of warping, shear, rotary inertia etc;Rao,1973