@article{SF_1976__13_134195,
     author = {S. Ligh},
     title = {On a class of semigroups admitting ring structure.},
     journal = {Semigroup forum},
     pages = {37--46},
     publisher = {mathdoc},
     volume = {13},
     year = {1976},
     zbl = {0348.20047},
     url = {http://geodesic.mathdoc.fr/item/SF_1976__13_134195/}
}