  We consider the recovery of a source term $f(x,t)=p(x)q(t)$ for the
nonhomogeneous heat equation in $\Omega\times (0,\infty)$ where $\Omega$ is a
bounded domain in $\mathbb{R}^2$ with smooth boundary $\partial\Omega$ from
overposed lateral data on a sparse subset of $\partial\Omega\times(0,\infty)$.
Specifically, we shall require a small finite number $N$ of measurement points
on $\partial\Omega$ and prove a uniqueness result; namely the recovery of the
pair $(p,q)$ within a given class, by a judicious choice of $N=2$ points.
Naturally, with this paucity of overposed data, the problem is severely
ill-posed. Nevertheless we shall show that provided the data noise level is
low, effective numerical reconstructions may be obtained.
