  Let A a regular F_p-algebra. The relative K-groups K_q(A[x]/(x^m),(x)) and
the Nil-groups Nil_q(A[x]/(x^m)) were evaluated earlier by the author and
Madsen in terms of the big de Rham-Witt groups of the ring A. In this paper, we
evaluate the maps of relative K-groups and Nil-groups induced by the canonical
projection from A[x]/(x^m) to A[x]/(x^n). The result depends strongly on the
prime p. It generalizes work of Stienstra on the groups in degrees 2 and 3.
