@article{DE_1967_3_1_a13,
     author = {S. V. Uspenskii},
     title = {Mixed derivatives of functions summable with a weight},
     journal = {Differencialʹnye uravneni\^a},
     pages = {139--154},
     year = {1967},
     volume = {3},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1967_3_1_a13/}
}