QHE and far infra-red properties of bilayer graphene in a strong magnetic field D. S.L. Abergel, E. McCann and V. I. Fal'ko Eur. Phys. J. Special Topics, 148 (2007) 105-115 Published online: 25 September 2007 DOI: 10.1140/epjst/e2007-00230-8