@article{SF_1974__6_133993,
     author = {J.E. Ault},
     title = {Semigroups with midunits.},
     journal = {Semigroup forum},
     pages = {346--351},
     publisher = {mathdoc},
     volume = {6},
     year = {1974},
     zbl = {0267.20060},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__6_133993/}
}