Period Solutions Of Delay Differential Equations With Multiple Lags

In our paper we mainly study the following differential delay equations (r_i are positive contants ). We translate this equation into Hamiltonian systems by changing variables and obtain the existence of period solutions using variational method . Then we extend the conclusions which are obtained by Fei Guihua [7] to another equationAt last we obtain the existence of period solutions of the differential delay equations(δ_i = 1 or -1) which is more general.