  An algorithm for the reduction of one-loop n-point tensor integrals to basic
integrals is proposed. We transform tensor integrals to scalar integrals with
shifted dimension and reduce these by recurrence relations to integrals in
generic dimension. Also the integration-by-parts method is used to reduce
indices (powers of scalar propagators) of the scalar diagrams. The obtained
recurrence relations for one-loop integrals are explicitly evaluated for 5- and
6-point functions. In the latter case the corresponding Gram determinant
vanishes identically for d=4, which greatly simplifies the application of the
recurrence relations.
