“…For some fundamental results in the theory of differential equations involving Caputo and Riemann-Liouville fractional derivatives, please see [1,2,24,32,33,34,41] and the references therein. Since Hilfer [18] proposed the generalized Riemann-Liouville fractional derivative, there has been some interest in studying differential equations involving Hilfer fractional derivatives (see [10,11,20] and the references therein). Recently, considerable attention has been given to the existence of solutions of initial and boundary value problems for fractional differential equations with Hilfer fractional derivative [5,35,36].…”