@article{DE_1970_6_9_a21,
     author = {I. N. Astafieva},
     title = {Second solutions of equations with positive operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1722--1724},
     publisher = {mathdoc},
     volume = {6},
     number = {9},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1970_6_9_a21/}
}