Minimal volume $k$-point lattice $d$-simplices

We extend the results of Bey, Hen, and Wills (http://arxiv.org/abs/math/0606089). In this paper, we show that, up to equivalence under unimodular transformations, there is exactly one class of $d$-simplices having $k\ge 1$ interior lattice points and minimal volume $\frac{1}{d!}(dk+1)$.