Conductivity in Two-Dimensional Disordered Model with Anisotropic   Long-Range Hopping
  We consider two-dimensional system of particles localized on randomly distributed sites of squared lattice with anisotropic transfer matrix elements between localized sites. By summing of "diffusion ladder" and "cooperon ladder" type vertices we calculated the conductivity for various sites and particles densities. 
E. A. Dorofeev and S. I. Matveenko