Precise determination of the conductivity exponent of 3D percolation using exact numerical renormalization J. P. Clerc, V. A. Podolskiy and A. K. Sarychev Eur. Phys. J. B, 15 3 (2000) 507-516 Published online: 15 June 2000 DOI: 10.1007/s100510051153