  We present a method to compute the density of states induced by N non
magnetic impurities in a d-wave superconductor, in the unitary limit of very
strong scatering centers. For frequencies very small as compared to the
superconducting gap ($\omega \ll \Delta_0$) the additional density of states
has the leading divergence ${\displaystyle \delta \rho (\omega) \simeq n_i / [
| 2 \omega | (\ln^2 |\omega/\Delta_0| + (\pi/2)^2)]}$. This result is non
perturbative.
