On a theorem by Treves
  According to a theorem of Treves, the conserved functionals of the KdV equation vanish on each formal Laurent series 1/x^2 + u0 + u2 x^2 + u3 x^3 + >... . We propose a new, very simple geometrical proof for this statement. 
Carlo Morosi (Politecnico di Milano), Livio Pizzocchero (Univ. di   Milano)