Problems (Raised at the Colloquium on Semigroups, Szeged, 15-19 August, 1994). M.B. Szendrei; G. Pollák — 1996 Semigroup forum
The translational hull of a subsemigroup of a semilattice of groups. G. Pollák; A. Ali Ismaeel — 1992 Semigroup forum