On the distribution of linear combinations of eigenvalues of the   Anderson model
  Probabilistic estimates on linear combinations of eigenvalues of the one dimensional Anderson model are derived. So far only estimates on the density of eigenvalues and of pairs were found by Wegner and by Minami. Our work was motivated by perturbative explorations of the Nonlinear Schroedinger Equation, where linear combinations of eigenvalues are the denominators and evaluation of their smallness is crucial. 
Shmuel Fishman, Yevgeny Krivolapov and Avy Soffer