[1] Bainov, D. D., Mishev, D. P.: Oscillation Theory for Neutral Equations with Delay. Adam Hilger IOP Pablisching Ltd. (1991) 288pp..
[2] Grammatikopoulos, M. K., Grove, E. A., Ladas, G.:
Oscillation and asymptotic behavior of second order neutral differential equations with deviating arguments. Canad. Math. Soc. V8 (1967) 153$-$161.
MR 0909906
[3] Graef, J. R., Grammatikopoulos, M. K., Spikes, P. W.: Asymptotic Properties of Solutions of Neutral Delay Differential Equations of the Second Order. Radovi Matematički $\ V_4\ $ (1988) 113 $-$149.
[4] Graef, J. R., Grammatikopoulos, M. K., Spikes, P. W.:
On the Asymptitic Behavior of Solutions of Second Order Nonlinear Neutral Delay Differential Equations. Journal Math. Anal. Appl. V156 $N_1$ (1991) 23$-$39.
MR 1102594
[5] Graef, J. R., Grammatikopoulos, M. K., Spikes, P. W.:
Asymptotic Behavior of Nonoscillatory Solutions of Neutral Delay Differential Equations of Arbitrary Order. Nonlinear Analysis, Theory, Math., Appl. V21, N1 (1993) 23$-$42.
MR 1231526
[6] Györi, I., Ladas, G.:
Oscillation Theory of Delay Differential Equations. Clear. Press., Oxford (1991) 368pp.
MR 1168471
[7] Jaroš, J., Kussano, T.:
Sufficient conditions for oscillations of higher order linear functional differential equations of neutral type. Japan J. Math.15 (1989) 415$-$432.
MR 1039249
[8] Jaroš, J., Kusano, T.:
Oscillation properties of first order nonlinear functional differential equations of neutral type. Diff. and Int. Equat. (1991) 425$-$436.
MR 1081192
[9] Kusano, T., Onose, H.:
Nonoscillation theorems for differential equation with deviating argument. Pacific J. Math. 63, $N_1$ (1976) 185$-$192.
MR 0417536