@article{2220, author = {Bergmann, Gustav}, title = {Multiplicative closures}, journal = {Portugaliae mathematica}, volume = {11}, year = {1952}, pages = {169-172}, zbl = {0048.02203}, mrnumber = {0052391}, language = {en}, url = {http://dml.mathdoc.fr/item/2220} }
Bergmann, Gustav. Multiplicative closures. Portugaliae mathematica, Tome 11 (1952) pp. 169-172. http://gdmltest.u-ga.fr/item/2220/