  This paper gives a new proof of a result of Geoghegan and Mihalik which
states that whenever a contractible open $n$-manifold $W$ which is not
homeomorphic to $\mathbf{R}^n$ is a covering space of an $n$-manifold $M$ and
either $n \geq 4$ or $n=3$ and $W$ is irreducible, then the group of covering
translations injects into the homeotopy group of $W$.
