@article{ZNSL_1971_21_a2,
     author = {A. V. Ivanov},
     title = {On some second order elliptic systems},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {34--41},
     publisher = {mathdoc},
     volume = {21},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1971_21_a2/}
}