@article{TMF_1989_81_1_a5,
     author = {N. E. Firsova and A. I. Sherstyuk},
     title = {Some properties of~generalized spectral problems associated with the {Schr\"odinger} equation},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {59--68},
     publisher = {mathdoc},
     volume = {81},
     number = {1},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1989_81_1_a5/}
}