  A detailed derivation of a two dimensional (2D) low energy effective model
for spinless fermions on a square lattice with local interactions is given.
This derivation utilizes a particular continuum limit that is justified by
physical arguments. It is shown that the effective model thus obtained can be
treated by exact bosonization methods. It is also discussed how this effective
model can be used to obtain physical information about the corresponding
lattice fermion system.
