“…This is a field under strong research, namely for optimal control problems, differential equations, biology, etc (see e.g. [10,11,16,17,20,27,30,33]). For some literature on what this paper concerns, we suggest the reader to [2,4,6,8,9,12,18,19,23,31] for fractional variational problems dealing with Caputo derivative, in [3] for Lagrangians depending on fractional integrals, and in [13,21] when presence of indefinite integrals.…”