%0 Journal Article
%A R. I. Grigorchuk
%T Superamenability and the problem of occurrence of free semigroups
%J Funkcionalʹnyj analiz i ego priloženiâ
%D 1987
%P 74-75
%V 21
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/FAA_1987_21_1_a10/
%G ru
%F FAA_1987_21_1_a10