Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by I. N. Belskaya, S. Fornasier, Yu. N. Krugly, V. G. Shevchenko, N. M. Gaftonyuk, M. A. Barucci, M. Fulchignoni and R. Gil-Hutton A&A, 515 (2010) A29 Published online: 03 June 2010 DOI: 10.1051/0004-6361/201013994