@article{DAN_1991_318_4_a15,
     author = {S. R. Umarov},
     title = {On the well-posedness of systems of pseudodifferential equations},
     journal = {Doklady Akademii Nauk},
     pages = {835--839},
     publisher = {mathdoc},
     volume = {318},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_318_4_a15/}
}