@article{VMUMM_1992_5_a4,
     author = {S. M. Ageev},
     title = {On extending the action},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {20--23},
     year = {1992},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1992_5_a4/}
}