Necessary and sufficient conditions for the oscillation of forced nonlinear second order differential equations with delayed argument

For a special class of the external force g(t) and nonnegative potential a(t), we give necessary and sufficient conditions for the oscillation of all solutions of a nonlinear second order forced differential equation with delayed argument of Emden-Fowler type in the form x ''(t) + a(t)\x(phi(t))\(nu) sgn x(phi(t)) = g(t) in the superlinear (nu > 1) and the sublinear cases (nu < 1). (C) 1997 Academic Press.