“…The use of Carleman estimates quickly became a powerful tool in many areas of PDEs, especially in both theoretical and numerical methods for inverse problems, see e.g., [5,4,16,7,9,19,26,29]. Carleman estimates were used in cloaking [28] and in the area of computing solution to Hamilton-Jacobi equations [20,27]. We recall a useful Carleman estimate which is important for us in the proof of the main theorem in this paper.…”