@article{DE_1989_25_11_a8,
     author = {A. Yu. Kolesov and E. F. Mishchenko},
     title = {A problem of {Pontryagin}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1888--1891},
     publisher = {mathdoc},
     volume = {25},
     number = {11},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_11_a8/}
}