“…The growing interest in the subject is due to its extensive applications in diverse fields such as physics, fluid mechanics, viscoelasticity, heat conduction in materials with memory, chemistry and engineering. Much of the work is devoted to the existence and uniqueness of solutions for fractional differential equations; see, for example, Kilbas et al [10], Miller and Ross [13], Podlubny [14], Zhou [22] and [1,5,19,21,23,24] and the references cited therein. Since Hilfer [9] proposed the generalized Riemann-Liouville fractional derivative (Hilfer fractional derivative), there has been shown some interest in studying evolution equations involving Hilfer fractional derivatives (see [2,4,7,8,18,20]).…”