Comment on "On the oscillation of fractional-order delay differential equations with constant coefficients" [Commun Nonlinear Sci 19(11) (2014) 3988-3993]

Abstract In this paper, some necessary and sufficient conditions are established for the oscillation of fractional-order delay differential equations with constant coefficients in the form: x ′ ( t ) + pD - α x ( t ) + qx ( t - τ ) = 0 , 0 α 1 , where D - α x ( t ) denotes the Liouville fractional derivatives on half-axis R + , p , q and τ are real constants. And also some oscillation results for the fractional-order neutral delay differential equations with constant coefficients in the form: - D - α ( x ( t ) + rx ( t - δ ) ) + qx ( t - τ ) = 0 , 0 α 1 , where D - α x ( t ) denotes the Liouville fractional derivatives on half-axis R + , q , r , τ and δ are real constants. The results obtained here correct and improve some known results in Bolat (2014).