  In this paper we study an inverse boundary value problem for the biharmonic
operator with first order perturbation. Our geometric setting is that of a
bounded simply connected domain in the Euclidean space of dimension three or
higher. Assuming that the inaccessible portion of the boundary is flat, and we
have knowledge of the Dirichlet-to-Neumann map on the complement, we prove
logarithmic type stability estimates for both the first and the zeroth order
perturbation of the biharmonic operator.
