Directed transport in quantum Hall bilayers R. Khomeriki, L. Tkeshelashvili, T. Buishvili and Sh. Revishvili Eur. Phys. J. B, 51 3 (2006) 421-424 Published online: 13 June 2006 DOI: 10.1140/epjb/e2006-00234-6