The self-consistent diagram approximation for lattice systems G. S. Bokun, Ya. G. Groda, V. V. Belov, C. Uebing and V. S. Vikhrenko Eur. Phys. J. B, 15 2 (2000) 297-304 Published online: 15 May 2000 DOI: 10.1007/s100510051128