[1] Foltynska I., Werbowski J.: On the oscillatory behaviour of solutions of systems of differential equations with deviating arguments. In. Qual. Theory Diff. Equat. Amsterdam (1981) 1, 243-256. MR 0680596

[2] Kondratev V. A.: On oscillation of solutions of the equation $y\sp{(n)}+p(x)y=0$. (in Russian). Trudy Mosk. Mat. O-stva, (1961), 10, 419-436. MR 0141842

[3] Marušiak P,: On the oscillation of nonlinear differential systems with retarded arguments. Math. Slovaca 34, N1 (1984), 73-88. MR 0735938

[4] Marušiak P.: Oscillatory properties of solutions of nonUnear differential systems with deviating arguments. Czech. Math. J. 36, N2 (1986), 223-231. MR 0831310

[5] Sficas Ch. K., Staikos V. A.: The effect of retarded actions on nonlinear oscillations. Proc. Araer. Math. Soc. 46 (1974), 256-264. MR 0355268 | Zbl 0263.34075

[6] Šeda V.: On nonlinear differential systems with deviating arguments. Czech. Math. J. 36, N3 (1986), 450-466. MR 0847772

[7] Shevelo V. N.: On oscillation of solutions of differential equations with deviating arguments. (in Russian), Kiev, 1978. MR 0492732

[8] Shevelo V. N., Varech N. V., Gritsai A. K.: Oscillatory properties of solutions of systems of differential equations with deviating arguments. (in Russian). Inst. Math. Ukr. Acad. of Sciences, Kiev (reprint) 85. 10 (1985), 3-46.

[9] Varech N. V., Shevelo V. N.: Asymptotic properties of components of solutions of certain many-dimensional systems with deviating arguments. (in Russian). In: Differential-functional equations and their applications. Inst. Math. Ukr. Acad, of Sciences, Kiev (1985), 108-124.