@article{DE_1971_7_7_a0,
     author = {N. V. Azbelev},
     title = {The zeros of the solutions of a second order linear differential equation with retarded argument},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1147--1157},
     publisher = {mathdoc},
     volume = {7},
     number = {7},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_7_a0/}
}