“…Let us finally mention that inverse problems for the semilinear Schrödinger operators and for nonlinear conductivity equations have been investigated intensively recently, see for example [15], [30], [31], [35], [25], [26], and [9], [21], [7], [8], [40], [43], respectively. Theorem 1.1 is a direct consequence of the main result of [19], combined with some boundary determination results of [38] and of Appendix A, as well as the higher order linearization procedure introduced in [28] in the hyperbolic case, and in [15], [31] in the elliptic case. We refer to [20] where the method of a first order linearization was pioneered in the study of inverse problems for nonlinear PDE, and to [3], [10], [44], and [45] where a second order linearization was successfully exploited.…”