Abstract
By using a generalized Riccati substitution, we present a new criterion for oscillation of solutions of fourth-order quasi-linear differential equations (r(t)(x'"(t))(alpha))' + f(t, x(sigma(t))) = 0, in noncanonical case integral(infinity) r(-1/alpha)(s)ds < infinity. We utilize an approach that gives rise to two or three independent conditions, eliminating non-oscillatory solutions. Moreover, we establish conditions in a non-traditional form (lim sup (.) > 1), while condition (lim sup (.) = infinity) cannot be applied. Our results essentially improve and complement a number of related ones. Examples are provided to illustrate the results. (C) 2020 Elsevier Inc. All rights reserved.