@article{UZKU_1954_114_8_a3,
     author = {P. G. Kontorovich},
     title = {On the theory of semigroups in a~group},
     journal = {U\v{c}\"enye zapiski Kazanskogo universiteta. Seri\^a Fiziko-matemati\v{c}eskie nauki},
     pages = {35--43},
     year = {1954},
     volume = {114},
     number = {8},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/UZKU_1954_114_8_a3/}
}