@article{VMUMM_2005_3_a4,
     author = {S. N. Berezinskaya and E. I. Kugushev and O. V. Sorokina},
     title = {Motion of mechanical systems with unilateral constraints},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {18--24},
     year = {2005},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2005_3_a4/}
}