Аннотация:Spases of double cosets of infinite symmetric groups
with respect to some special subgroups admit natural structures
of semigroups. Elements of such semigroups can be interpreted in
combinatorial terms. We present a desription of such constructions
in a relatively wide degree of generality.
ftp://ftp.pdmi.ras.ru/pub/publicat/znsl/v462/p065.pdf