@article{DAN_1971_197_4_a15,
     author = {S. A. Chunikhin},
     title = {Indexials and subgroups},
     journal = {Doklady Akademii Nauk},
     pages = {798--800},
     publisher = {mathdoc},
     volume = {197},
     number = {4},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_197_4_a15/}
}