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

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-αx(t)+qx(t-τ)=0,0<α<1,where D-αx(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-αx(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).