  For an initial-boundary value problem for a parabolic equation in the spatial
variable $x=(x_1,.., x_n)$ and time $t$, we consider an inverse problem of
determining a coefficient which is independent of one spatial component $x_n$
by extra lateral boundary data. We apply a Carleman estimate to prove a
conditional stability estimate for the inverse problem. Also we prove similar
results for the corresponding inverse source problem.
