“…Indeed, for example, in the work [15] the authors gave the solution of conformable-fractional telegraph equations in terms of the classical exponential function, however for the Caputo-fractional telegraph equations considered in the very good papers [19,20,36], the fundamental solution cannot be given in terms of the exponential function as in the conformable-fractional case, and therefore the authors have been introduced the so-called Mittag-Leffler function. Another comparison, we notice that the constants of increases of the norms of the control bounded operators W and W −1 in the application of the work [27] are given directly in a simple way in terms of the exponential function, contrary, for the Caputo fractional derivative in the application of the nice work [51] these constants are given in terms of the so-called Mittag-Leffler function. For more details and conclusions concerning the uses and applications of conformable fractional calculus, we refer to the works [2,4,5,7,8,10,11,12,13,14,16,17,22,23,24,25,28,29,42,49].…”