Modelling the molecular Zeeman-effect in M-dwarfs: methods and first results D. Shulyak, A. Reiners, S. Wende, O. Kochukhov, N. Piskunov and A. Seifahrt A&A, 523 (2010) A37 Published online: 15 November 2010 DOI: 10.1051/0004-6361/201015229