“…Since Bukhgeim and Klibanov [12], their methodology has been developed for various equations and we can refer to many papers on inverse problems of determining spatially varying coefficients and components of source terms. As a partial list of references on inverse problems for hyperbolic and parabolic equations by Carleman estimates, we refer to Baudouin and Yamamoto [3], Bellassoued [5], [6], Bellassoued and Yamamoto [8], Benabdallah, Cristofol, Gaitan and Yamamoto [11], Cristofol, Gaitan and Ramoul [16], Imanuvilov and Yamamoto [31] - [34], Klibanov [43], [44], Klibanov and Yamamoto [47], Yamamoto [57], Yuan and Yamamoto [60].…”