@article{FAA_1987_21_1_a10,
     author = {R. I. Grigorchuk},
     title = {Superamenability and the problem of occurrence of free semigroups},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {74--75},
     publisher = {mathdoc},
     volume = {21},
     number = {1},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1987_21_1_a10/}
}