@article{DAN_1994_337_5_a13,
     author = {M. V. Shamolin},
     title = {A new two-parameter family of phase portraits in the problem of},
     journal = {Doklady Akademii Nauk},
     pages = {611--614},
     year = {1994},
     volume = {337},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1994_337_5_a13/}
}