  We establish a logarithmic stability inequality for the inverse problem of
determining the non linear term, appearing in a semilinear BVP, from the
corresponding Dirichlet-to-Neumann map (abbreviated to DtN map in the rest of
this text). Our result can be seen as a stability inequality for an earlier
uniqueness result by Isakov and Sylvester [Commun. Pure Appl. Math. 47 (1994),
1403-1410].
