1. S. R. Grace andB. S. Lalli, Oscillation theorems fornth order nonlinear differential equations with deviating arguments,Proc. Amer. Math. Soc.,90 (1984), 65–70.
2. S. R. Grace andB. S. Lalli, Oscillatory and asymptotic behavior of solutions of differential equations with deviating arguments,J. Math. Anal. Appl.,104 (1984), 79–94.
3. S. R. Grace andB. S. Lalli, Oscillation theorems fornth order delay differential equations,J. Math. Anal. Appl. 91 (1983), 352–366.
4. I. V. Kamenev, Oscillation of solutions of a second order differential equation with “integrally small” coefficient,Differencial'nye Uravnenija,13 (1977), 1491–1497. (In Russian).
5. Lecture Notes in Pure and Applied Math.;A. G. Kartsatos,1977