M. Cacciari, S. Frixione, M. Mangano, P. Nason, и G. Ridolfi. (2008)cite arxiv:0804.2800
Comment: Updated description of comparison with 0804.1476. Improvements in
text and update of published references. No changes in results. Version to
appear in JHEP. v3 fixes a typo in the authors' list.