@article{DE_1991_27_4_a19,
     author = {V. A. Il'in and E. I. Moiseev},
     title = {A mean-value formula for root functions of the {Schr\"odinger} operator},
     journal = {Differencialʹnye uravneni\^a},
     pages = {702--705},
     publisher = {mathdoc},
     volume = {27},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_4_a19/}
}