@article{SF_1971__3_133844,
     author = {N. Bernstein},
     title = {Group-like semigroups.},
     journal = {Semigroup forum},
     pages = {58--63},
     publisher = {mathdoc},
     volume = {3},
     year = {1971},
     zbl = {0241.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1971__3_133844/}
}