@article{SF_1982__24_134551,
     author = {E.D. Ljapin},
     title = {Identities valid globally in semigroups.},
     journal = {Semigroup forum},
     pages = {263--270},
     year = {1982},
     volume = {24},
     url = {http://geodesic.mathdoc.fr/item/SF_1982__24_134551/}
}