[1] D. V. Izymova: On the conditions of oscillation and nonoscillation of solutions of nonlinear second order differential equations. Дифференциальные уравнения 2 (1966), 1572-1586.
[2] B. Mehri:
On the conditions for the oscillation of solutions of nonlinear third order differential equations. Čas. pěst. mat. 101 (1976), 124-129.
MR 0442366
[3] J. S. W. Wang: On second order nonlinear oscillation. Math. Research Center, University of Wisconsin Technical Report No. 836, Also Funkcial Eknoc. 11 (1969), 207-23.