“…With the development of modern tools such as primitive divisor theorem, modular approach, or computational techniques, many authors investigated the above equation when k ≥ 1, see for example [1,2,3,7,11,13,14,15,16,17,18,19,20,22]. Especially, the cases (p 1 , p 2 , p 3 ) = (2,3,11), (2,11,19), (2,3,19), (2,3,17), (5,13,17) are considered in [6,9,10,11] and [21], respectively. For more information and the rich literature on equation (1), we refer to an excellent survey [12] and the 359 references therein.…”