@article{GDZPPN001254138, title = {A new notion in the theory of semigroups.}, journal = {Semigroup forum}, volume = {20}, year = {1980}, pages = {233-240}, zbl = {0439.20045}, url = {http://dml.mathdoc.fr/item/GDZPPN001254138} }
Satko, L.; Grosek, O. A new notion in the theory of semigroups.. Semigroup forum, Tome 20 (1980) pp. 233-240. http://gdmltest.u-ga.fr/item/GDZPPN001254138/