Random walks with imperfect trapping in the decoupled-ring approximation T. Aspelmeier, J. Magnin, W. Graupner and U. C. Täuber Eur. Phys. J. B, 28 4 (2002) 441-450 Published online: 13 August 2002 DOI: 10.1140/epjb/e2002-00247-1