Model atmosphere analysis of the extreme DQ white dwarf GSC2U J131147.2+292348 D. Carollo, D. Koester, A. Spagna, M. G. Lattanzi and S. T. Hodgkin A&A, 400 1 (2003) L13-L16 Published online: 24 February 2003 DOI: 10.1051/0004-6361:20030132