@article{DE_1992_28_8_a0,
     author = {L. V. Kritskov},
     title = {Representation and estimates of root functions of singular differential operators on an interval. {I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1291--1302},
     publisher = {mathdoc},
     volume = {28},
     number = {8},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_8_a0/}
}