1. Nonlinear oscillation of fourth order differential equations;Kusano;Can. J. Math.,1976
2. Extremal solutions for a class of nonlinear differential equations;Kreith;Proc. Am. math. Soc.,1980
3. EDelson A.L. & SChuur J.D., Nonoscillatory solutions of (rx(n))(n)±⨍(t, x)x=0, Pacif. J. Math. (to appear).
4. EDelson A.L. & PErri E., Asymptotic behavior of nonoscillatory equations, preprint.
5. Oscillation properties of solutions of certain ordinary differential equations;Kiguradze;Dokl. Akad. Nauk. SSSR,1962