@article{GDZPPN001252275, title = {Semigroups in which each -class contains at most one regular ...-class.}, journal = {Semigroup forum}, volume = {14}, year = {1977}, pages = {91-92}, zbl = {0372.54035}, url = {http://dml.mathdoc.fr/item/GDZPPN001252275} }
Magill, K. D. jr. Semigroups in which each -class contains at most one regular ...-class.. Semigroup forum, Tome 14 (1977) pp. 91-92. http://gdmltest.u-ga.fr/item/GDZPPN001252275/