On the spectrum of the monodromy operator for slowly oscillating periodic solutions of functional differential equations with several delays

In this paper the hyperbolicity of the periodic solutions of a class of functional differential equations with several delays is studied. It is proved that this problem can be reduced to the investigation of zeros of some associated analytic function. This result is an extension of an analogous result obtained by H.-O. Walther and A. L. Skubachevskiĭ [Tr. Mosk. Mat. Obs. {bf 64} (2003), 3--53; [msn] MR2030185 (2005m:34167) [/msn]] for the case when the equation contains only one delay.