@article{DAN_1976_228_4_a1,
     author = {S. N. Antontsev},
     title = {On a problem of {M.\,A.~Lavrent'ev}},
     journal = {Doklady Akademii Nauk},
     pages = {772--775},
     publisher = {mathdoc},
     volume = {228},
     number = {4},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1976_228_4_a1/}
}