Connection between Sylow subgroups of symmetric group and their semigroups of endomorphismPuusemp, PeeterEesti Teaduste Akadeemia Toimetised. Füüsika. Matemaatika1993 / 2, lk. 144-156 On the torsion subgroups and endomorphism semigroups of abelian groupsPuusemp, PeeterAlgebras, groups and geometries1997 / p. 407-422