@article{ Solr-acta14684, title = {Characterizations of completely regular elements in semigroups}, series = {Acta scientiarum mathematicarum}, author = {Lajos Sándor}, year = {1978}, url = {http://acta.bibl.u-szeged.hu/14684/1/math_040_fasc_003_004_297-300.pdf} }