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291similar to one used in [5], upon examining the paper [5], we find that control systems are different from the system given above by (1) and (21). REFERENCES [ 11 EJ. Davison and D. Ball ''On the mnuollabihty of perturbed controllable SYStmS" I21 EJ. Davison and EO. Kunze, "Some suffiaent conditions for the global and local IEEE T m . Auromal. C h r . (Cmresp.), voL, AC-17, pp. 825-826, Dec. 1972. . _ controllability of nonlinear time-varying system%" SIAM J. Contr., vol. 8 , no. 4, pp. [3] L.V. Kantoroy'ch and G9. Akilov. F U R C~~O M~ Analysis in Nonned Spaces. New 489.498, 1970. York: Ma& 1964. 141 J. Klamka, "On the global controllability of perturbed nonlinear systems." IEEE 1-51 KB. Mina and B.F.' Womack, "On the conikllability of a class of nonlinear T r m . A u t o W . Conrr. vol. AC-20, pp. 170-172 Feb. 1975. systems," IEEE T r m . A u I o m t Abstmct--The limitations of the describing function method (liwarizatioa method) for nornear system stabiility~anaiysis are eonsidered. An example proposed by Dewey to m t e the erroneous result due to the misuse of des~ribing f d o n methad i~ considered.

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