Liquid crystal helical ribbons as isometric textures M.-F. Achard, M. Kleman, Yu. A. Nastishin and H.-T. Nguyen Eur. Phys. J. E, 16 1 (2005) 37-47 Published online: 31 January 2005 DOI: 10.1140/epje/e2005-00005-2