  We consider the massless two-loop two-point function with arbitrary powers of
the propagators and derive a representation, from which we can obtain the
Laurent expansion to any desired order in the dimensional regularization
parameter eps. As a side product, we show that in the Laurent expansion of the
two-loop integral only rational numbers and multiple zeta values occur. Our
method of calculation obtains the two-loop integral as a convolution product of
two primitive one-loop integrals. We comment on the generalization of this
product structure to higher loop integrals.
