@article{VMUMM_2021_3_a5,
     author = {I. N. Sergeev},
     title = {The definition of the indices of oscillation, rotation, and wandering of nonlinear differential systems},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {41--46},
     publisher = {mathdoc},
     number = {3},
     year = {2021},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2021_3_a5/}
}