  A generalized variant of the Calder\'on problem from electrical impedance
tomography with partial data for anisotropic Lipschitz conductivities is
considered in an arbitrary space dimension $n \geq 2$. The following two
results are shown: (i) The selfadjoint Dirichlet operator associated with an
elliptic differential expression on a bounded Lipschitz domain is determined
uniquely up to unitary equivalence by the knowledge of the Dirichlet-to-Neumann
map on an open subset of the boundary, and (ii) the Dirichlet operator can be
reconstructed from the residuals of the Dirichlet-to-Neumann map on this
subset.
