“…Fractional derivative arises from many physical processes, such as a charge transport in amorphous semiconductors [22], electrochemistry and material science, they are in fact described by differential equations of fractional order [9,10,17,18]. Recently, many studies on fractional differential equations, involving different operators such as Riemann-Liouville operators [19,24], Caputo operators [1,3,13,25], Hadamard operators [23] and q−fractional operators [2], have appeared during the past several years. Moreover, by applying different techniques of nonlinear analysis, many authors have obtained results of the existence and uniqueness of solutions for various classes of fractional differential equations, for example, we refer the reader to [3-8, 11, 12, 14, 15, 19] and the references cited therein.…”