Exact solution and magnetic properties of an anisotropic spin ladder Zu-Jian Ying, Itzhak Roditi, Angela Foerster and Bin Chen Eur. Phys. J. B, 41 1 (2004) 67-74 Published online: 30 September 2004 DOI: 10.1140/epjb/e2004-00295-5