  Applications of the integrable system techniques to the non-equilibrium
transport problems are discussed. We describe one-dimensional electrons
tunneling through a point-like defect either by the s-d exchange (Kondo)
mechanism, or via the resonanse level (Anderson) mechanism. These models are
potential candidates to be solved exactly in the presence of arbitrary external
bias. We draw attention also to several mesoscopical systems which can be
tackled by the massless form-factor approach, as perturbations of integrable
models. The basic unperturbed model is the massless sine-Gordon model with the
interaction (cosine) term restricted to one point, which is integrable. It is
being perturbed by the second interaction term, which destroys integrability.
Quasi-exact results can be obtained by making use of the basis of massless
quasiparticles of the sine-Gordon model.
