Oscillation criteria for certain fourth order nonlinear functional differential equations

Some new criteria for the oscillation of the fourth order functional differential equation ddt(1a3(t)(ddt1a2(t)(ddt1a1(t)(ddtx(t))α1)α2)α3)+δq(t)f(x[g(t)])=0, where δ=±1δ=±1 are established.