@article{DE_1966_2_8_a2,
     author = {A. N. Erugin},
     title = {On extremals},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1027--1030},
     publisher = {mathdoc},
     volume = {2},
     number = {8},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_8_a2/}
}