1. W. Prager, Theory of structures, Brown University mimeographed notes, 1944.
2. S. Timoshenko, Vibration problems in engineering, D. Van Nostrand Company, Inc., New York, 1937, p. 341.
3. H. Lo, A non-linear problem in the bending vibration of a rotating beam, Journal of Applied Mechanics, American Society of Mechanical Engineers, 19, 461-465, (1952).
4. H. Lo and J. Renbarger, Bending vibrations of a rotating beam, First U. S. National Congress of Applied Mechanics, American Society of Mechanical Engineers, 1952, p. 75.