Magnetic susceptibility of an exactly solvable anisotropic spin ladder system A. P. Tonel, S. R. Dahmen, A. Foerster and A. L. Malvezzi Europhys. Lett., 64 1 (2003) 111-117 Published online: 01 November 2003 DOI: 10.1209/epl/i2003-00144-3