1. Differential equations of motion for combined flapwise bending, chordwise bending, and torsion of twisted non-uniform rotor blades;Houbolt;NASA Report 1346,1958
2. Die Berechnung der Drehschwingungen;Holzer,1921
3. New method of calculating natural modes of coupled bending-torsion vibration of beams;Myklestad;Transactions of the American Society of Mechanical Engineers,1945
4. Matrix solution of vibration of nonuniform beams;Thomson;Journal of Applied Mechanics,1950
5. Four pole parameters in vibration analysis;Molloy,1958