Dust grain growth in the interstellar medium of 5 < z < 6.5 quasars M. J. Michałowski, E. J. Murphy, J. Hjorth, D. Watson, C. Gall and J. S. Dunlop A&A, 522 (2010) A15 Published online: 27 October 2010 DOI: 10.1051/0004-6361/201014902