On the oscillation of fourth-order delay differential equations

In the paper, fourth-order delay differential equations of the form (r₃ (r₂ (r₁y' )' )' )'(t) + q(t) y ( τ (t) ) = 0 under the assumption ∫ _t₀∞dtrᵢ(t) < ∞ , i = 1,2,3, are investigated. Our newly proposed approach allows us to greatly reduce a number of conditions ensuring that all solutions of the studied equation oscillate. An example is also presented to test the strength and applicability of the results obtained.