Asymptotic behaviour of the nonoscillatory solutions of differential equations of second order with delay depending on the unknown function

The asymptotic behaviour of the solutions of the differential equations (r(t)x′(t))′ + f(t,x(t),x(Δ(t,x(t)))) = 0 in the case when ∫∞ dsr(s)=+∞ is considered.