1. Marchenko, VA: Expansion in eigenfunctions of non-selfadjoint singular second order differential operators. Mat. Sb. 52, 739-788 (1960) (in Russian)
2. Rofe-Beketov, FS: Expansion in eigenfunctions of infinite systems of differential equations in the non-selfadjoint and selfadjoint cases. Mat. Sb. 51, 293-342 (1960) (in Russian)
3. Guseinov, GS: Determination of an infinite non-selfadjoint Jacobi matrix from its generalized spectral function. Mat. Zametki 23, 237-248 (1978). English transl.: Math. Notes 23, 130–136 (1978)
4. Guseinov, GS: The inverse problem from the generalized spectral matrix for a second order non-selfadjoint difference equation on the axis. Izv. Akad. Nauk Azerb. SSR Ser. Fiz.-Tekhn. Mat. Nauk 5, 16-22 (1978) (in Russian)
5. Kishakevich, YL: Spectral function of Marchenko type for a difference operator of an even order. Mat. Zametki 11, 437-446 (1972). English transl.: Math. Notes 11, 266–271 (1972)