@article{DE_1973_9_3_a4,
     author = {R. S. Levitin},
     title = {The uniqueness of $O$-curves in a normal domain of the second kind},
     journal = {Differencialʹnye uravneni\^a},
     pages = {437--448},
     publisher = {mathdoc},
     volume = {9},
     number = {3},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_3_a4/}
}