@article{GDZPPN001257919, title = {The characterisation of monoids by properties of their S-systems.}, journal = {Semigroup forum}, volume = {31}, year = {1985}, pages = {251-266}, zbl = {0571.20067}, url = {http://dml.mathdoc.fr/item/GDZPPN001257919} }
Gould, V. The characterisation of monoids by properties of their S-systems.. Semigroup forum, Tome 31 (1985) pp. 251-266. http://gdmltest.u-ga.fr/item/GDZPPN001257919/