“…Recently a series of new results in approximation of solutions to the nonlinear fractional differential systems (FDS) of the Caputo type was published. Authors suggested a so-called "successive approximations technique" [19] to construct approximate solutions of the studied systems by incorporating also different types of linear [2,8,9,11] and nonlinear boundary conditions [10,12]. This approach demonstrates its effectiveness also when dealing with highly nonlinear systems, systems of a general order p ∈ (m, m + 1) or mixed order equations (see discussions in [3,4,8,9]).…”