@article{DE_1989_25_11_a4,
     author = {V. E. Volkov},
     title = {Boundedness of the number of orthogonal solutions of the equation $-u''+q(x)u=\lambda u$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1862--1866},
     publisher = {mathdoc},
     volume = {25},
     number = {11},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_11_a4/}
}