Asymptotic behavior of solutions of second order quasilinear differential equations with delay depending on the unknown function

The asymptotic behavior of the nonoscillatory solutions of quasilinear differential equations of second order with delay depending on the unknown function is considered. The main results given by [Bainov et al. (J. Comput. Appl. Math. 91 (1998) 87–96) and Wong (Funkcial. Ekvac. 11 (1968) 207–234)] are improved and generalized.