@article{MZM_1992_51_6_a13,
     author = {E. L. Tsvetkov},
     title = {Solvability and spectrum of the third boundary problem for an elliptic differential-difference equation},
     journal = {Matemati\v{c}eskie zametki},
     pages = {107--114},
     publisher = {mathdoc},
     volume = {51},
     number = {6},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_6_a13/}
}