Visible spectroscopy of 2003 UB313: evidence for N2 ice on the surface of the largest TNO? J. Licandro, W. M. Grundy, N. Pinilla-Alonso and P. Leisy A&A, 458 1 (2006) L5-L8 Published online: 16 October 2006 DOI: 10.1051/0004-6361:20066028