  We study the impedance boundary map (or Robin-to-Robin map) for the
Schrodinger equation in open bounded demain at fixed energy in multidimensions.
We give global stability estimates for determining potential from these
boundary data and, as corollary, from the Cauchy data set. Our results include
also, in particular, an extension of the Alessandrini identity to the case of
the impedance boundary map.
