On-site repulsion as the source of pairing in carbon nanotubes and intercalated graphite E. Perfetto, G. Stefanucci and M. Cini Eur. Phys. J. B, 30 2 (2002) 139-142 Published online: 29 November 2002 DOI: 10.1140/epjb/e2002-00367-6