@article{DAN_1991_321_5_a3,
     author = {A. Dzhuraev},
     title = {Some first-order nonelliptic overdetermined systems and their},
     journal = {Doklady Akademii Nauk},
     pages = {885--891},
     publisher = {mathdoc},
     volume = {321},
     number = {5},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_321_5_a3/}
}