@article{DE_1971_7_8_a2,
     author = {V. Ya. Derr},
     title = {On the question of the sign of the {Green's} function of a difference problem with combined boundary value conditions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1368--1376},
     year = {1971},
     volume = {7},
     number = {8},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_8_a2/}
}