@article{VMUMM_2019_1_a3,
     author = {I. N. Sergeev},
     title = {Oscillation, rotatability, and wandering characteristic indicators for differential systems determining rotations of plane},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {21--26},
     publisher = {mathdoc},
     number = {1},
     year = {2019},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2019_1_a3/}
}