@article{VMUMM_1993_5_a0,
     author = {V. V. Filippov},
     title = {An investigation of stationary points in a plane},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {3--11},
     publisher = {mathdoc},
     number = {5},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1993_5_a0/}
}