@article{SM_1993_75_2_a1,
     author = {L. D. Pustyl'nikov},
     title = {On the spectrum of the~discrete inhomogeneous wave equation, and vibrations of a~discrete string},
     journal = {Sbornik. Mathematics},
     pages = {317--331},
     year = {1993},
     volume = {75},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1993_75_2_a1/}
}