@article{DE_2005_41_6_a9,
     author = {S. A. Aldashev},
     title = {A {Criterion} for the {Existence} of {Eigenfunctions} of the {Darboux{\textendash}Protter} {Spectral} {Problem} for},
     journal = {Differencialʹnye uravneni\^a},
     pages = {795--801},
     year = {2005},
     volume = {41},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2005_41_6_a9/}
}