@article{DE_1981_17_8_a10,
     author = {D. Safarov},
     title = {Periodic solutions of first-order elliptic systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1468--1477},
     publisher = {mathdoc},
     volume = {17},
     number = {8},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1981_17_8_a10/}
}