[1] ERBE L.: Oscillation criteria for second order nonlinear delay equations. Canad. Math. Bull. 16 (1973), 49-56. MR 0324173 | Zbl 0272.34095

[2] ERBE L.: Oscillation and asymptotic behavior of solutions of third order differential delay equations. SIAM J. Math. Anal. 7 (1976), 491-500. MR 0433001 | Zbl 0356.34086

[3] HILLE E.: Non-oscillation theorems. Trans. Amer. Math. Soc. 64 (1948), 234-258. MR 0027925 | Zbl 0031.35402

[4] HARTMAN P., WINTNER A.: Linear differential and difference equations with monotone solutions. Amer. J. Math. 75 (1953), 731-743. MR 0057404 | Zbl 0051.07105

[5] KIGURADZE I. T.: On the oscillation of solutions of the equation $d^m u/dt^m +a(t)|u|^n \sgn u = 0$. (Russian), Mat. Sb. 65 (1964), 172-187. MR 0173060 | Zbl 0135.14302

[6] KITAMURA Y., KUSANO T.: Nonlinear oscillation of higher-order functional differential equations with deviating arguments. J. Math. Anal. Appl. 77 (1980), 100-119. MR 0591264 | Zbl 0465.34044

[7] KUSANO T., NAITO M.: Oscillation criteria for general linear ordinary differential equations. Pacific J. Math. 92 (1981), 345-355. MR 0618070 | Zbl 0475.34019

[8] KUSANO T., NAITO M.: Comparison theorems for functional differential equations with deviating arguments. J. Math. Soc. Japan 3 (1981), 509-532. MR 0620288 | Zbl 0494.34049

[9] MAHFOUD W. E.: Comparison theorems for delay differential equations. Pacific J. Math. 83 (1979), 187-197. MR 0555047 | Zbl 0441.34053

[10] TANAKA K.: Asymptotic analysis of odd order ordinary differential equations. Hiroshima Math. J. 10 (1980), 391-408. MR 0577867 | Zbl 0453.34033

[11] TRENCH W. F.: Canonical forms and principal systems for general disconjugate equations. Trans. Amer. Math. Soc. 189 (1974), 319-327. MR 0330632 | Zbl 0289.34051