@article{DE_1982_18_2_a23,
     author = {T. V. Treneva},
     title = {On a four-dimensional not strongly elliptic system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {351--353},
     publisher = {mathdoc},
     volume = {18},
     number = {2},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1982_18_2_a23/}
}