Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{SF_1979__18_134344, author = {A.H. Clifford}, title = {The free completely regular semigroup on a set.}, journal = {Semigroup forum}, pages = {87--92}, publisher = {mathdoc}, volume = {18}, year = {1979}, zbl = {0462.20047}, url = {http://geodesic.mathdoc.fr/item/SF_1979__18_134344/} }
A.H. Clifford. The free completely regular semigroup on a set.. Semigroup forum, Tome 18 (1979), pp. 87-92. http://geodesic.mathdoc.fr/item/SF_1979__18_134344/