  In this paper, by employing fixed-point methods, we obtain the existence and
uniqueness results for the nonlinear implicit fractional differential equations
in Banach spaces. Further, we obtain the uniqueness, dependence of the solution
on the initial condition as well as on the functions involved on the right-hand
side by means of Picard and weakly Picard operator theory and
Pompeiu--Hausdorff functional.
