6Holmes P J.Marsden J.A partial differential equation with infinitely many periodic Orbits,Chaotic oscillations of a forced beam,Arch Rat Mech Anal,1981,76:135-166.
7Abbyankar N S,et al.Chaotic vibrations of beams numerical solution of partial differential equations.Trans ASME.J of Applied Mechanics,1993,60:167-174.