  We generalize a theorem of Burde and de Rham characterizing the zeros of the
Alexander polynomial. Given a representation of a knot group $\pi$, we define
an extension of $\pi$, the Crowell group. For any GL(n,C) representation of
$\pi$, the zeros of the associated twisted Alexander polynomial correspond to
representations of the Crowell group into the group of dilations of C^n.
