@article{DE_1977_13_7_a6,
     author = {G. E. Popov},
     title = {A class of integrable systems with a small parameter},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1214--1217},
     publisher = {mathdoc},
     volume = {13},
     number = {7},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_7_a6/}
}