@article{DAN_1989_309_3_a0,
     author = {A. T. Bulabaev and L. A. Shuster},
     title = {On the theory of {Sturm{\textendash}Liouville} difference equations},
     journal = {Doklady Akademii Nauk},
     pages = {521--524},
     year = {1989},
     volume = {309},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1989_309_3_a0/}
}