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Three comparison theorems are established for the oscillation of the second-order neutral differential equations of mixed type $$ ig(r(t)[x(t)+p_1(t)x(t-sigma_1)+p_2(t)x(t+sigma_2)]'ig)' +q_1(t)x(t-sigma_3) +q_2(t)x(t+sigma_4)=0. $$ Our results are new even when $p_2(t)=q_2(t)=0$. An example is provided to illustrate the main results.