  Using the path-integral bosonization procedure at Finite Temperature we study
the equivalence between a massive Thirring model with non-local interaction
between currents (NLMT) and a non-local extension of the sine-Gordon theory
(NLSG). To this end we make a perturbative expansion in the mass parameter of
the NLMT model and in the cosine term of the NLSG theory in order to obtain
explicit expressions for the corresponding partition functions. We conclude
that for certain relationship between NLMT and NLSG potentials both the
fermionic and bosonic expansions are equal term by term. This result
constitutes a generalization of Coleman's equivalence at T=0, when considering
a Thirring model with bilocal potentials in the interaction term at Finite
Temperature. The study of this model is relevant in connection with the physics
of strongly correlated systems in one spatial dimension. Indeed, in the
language of many-body non-relativistic systems, the relativistic mass term can
be shown to represent the introduction of backward-scattering effects.
