Hallberg, K. A. Max Planck Institute for the Physics of Complex Systems, Max Planck Society;
http://arxiv.org/pdf/cond-mat/9505132.pdf (Preprint)
Hallberg, K. A., Horsch, P., & Martínez, G. (1995). Numerical renormalization group study of the correlation functions of the antiferromagnetic spin-1/2 Heisenberg chain. Physical Review B, 52(2), R719-R722. doi:10.1103/PhysRevB.52.R719.