%A Fabrici Igor %N 3-4 %P 271-275 %D 1969 %L acta14233 %O Bibliogr.: 275. p. %K TermĂŠszettudomĂĄny, Matematika, MĹąvelĹdĂŠs %T On invertible elements in compact semigroups %J Acta scientiarum mathematicarum %V 30