@article{DE_1968_4_9_a6,
     author = {L. A. Chelysheva},
     title = {On the theory of generalized characteristic numbers},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1616--1624},
     publisher = {mathdoc},
     volume = {4},
     number = {9},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_9_a6/}
}