  We investigate the effects of mesoscopic inhomogeneities on the
metal-superconductor transition occurring in several two-dimensional electron
systems. Specifically, as a model of systems with mesoscopic inhomogeneities,
we consider a random-resistor network, which we solve both with an exact
numerical approach and by the effective medium theory. We find that the width
of the transition in these two-dimensional superconductors is mainly ruled by
disorder rather than by fluctuations. We also find that "tail" features in
resistivity curves of interfaces between LaAlO3 or LaTiO3 and SrTiO3 can arise
from a bimodal distribution of mesoscopic local Tc's and/or substantial space
correlations between the mesoscopic domains.
