@article{DE_1968_4_2_a18,
     author = {V. N. Laptinskii},
     title = {A certain inequality},
     journal = {Differencialʹnye uravneni\^a},
     pages = {368--369},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_2_a18/}
}