@article{GDZPPN001255371, title = {Symmetrisations of semigroups.}, journal = {Semigroup forum}, volume = {24}, year = {1982}, pages = {67-76}, zbl = {0505.20042}, url = {http://dml.mathdoc.fr/item/GDZPPN001255371} }
Osondu, K.E. Symmetrisations of semigroups.. Semigroup forum, Tome 24 (1982) pp. 67-76. http://gdmltest.u-ga.fr/item/GDZPPN001255371/