Voir la notice de l'article provenant de la source Czech Digital Mathematics Library
@article{MASLO_1961__11_1_a0, author = {Wiegold, James}, title = {Semigroup {Coverings} of {Groups}}, journal = {Mathematica slovaca}, pages = {3--13}, publisher = {mathdoc}, volume = {11}, number = {1}, year = {1961}, mrnumber = {0158946}, zbl = {0104.01902}, language = {en}, url = {http://geodesic.mathdoc.fr/item/MASLO_1961__11_1_a0/} }
Wiegold, James. Semigroup Coverings of Groups. Mathematica slovaca, Tome 11 (1961) no. 1, pp. 3-13. http://geodesic.mathdoc.fr/item/MASLO_1961__11_1_a0/