Real space renormalization group with effective interactions: applications to 2-D spin lattices M. Al Hajj, N. Guihéry, J.-P. Malrieu and B. Bocquillon Eur. Phys. J. B, 41 1 (2004) 11-21 Published online: 30 September 2004 DOI: 10.1140/epjb/e2004-00288-4