On the Integrability of the Discrete Nonlinear Schroedinger Equation
  In this letter we present an analytic evidence of the non-integrability of the discrete nonlinear Schroedinger equation, a well-known discrete evolution equation which has been obtained in various contexts of physics and biology. We use a reductive perturbation technique to show an obstruction to its integrability. 
Decio Levi, Matteo Petrera, Christian Scimiterna