“…The concept of snap-back repellers is not new, but it is still the subject of intensive study. Some works that appeared in the last ten years are [Chen et al, 2016, Peng, 2007, Ren et al, 2017, Salman et al, 2016, Shi and Yu, 2008, Yuan et al, 2011, Zhao and Li, 2016. Note that differentiability of the map is an essential condition for Theorem 1, but see Gardini and Tramontana [2010a,b] for results which do not require smoothness.…”