Below is the ascii version of the abstract for 13-78.
The html version should be ready soon.
Vitaly Volpert, Vitali Vougalter
Solvability conditions for some non Fredholm operators in a layer in four
ABSTRACT. We study solvability in H^2 of certain linear nonhomogeneous elliptic problems involving the sum of the periodic Laplacian and a Schroedinger operator without Fredholm property and prove that under reasonable technical conditions the convergence in L^2 of their right sides implies the existence and the convergence in H^2 of the solutions.
We generalize the methods of spectral and scattering theory for
Schroedinger type operators from our preceding work.