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@article{SF_1974__6_133980, author = {A.H. Clifford and T.E. Hall}, title = {A characterization of ...-classes of semigroups as partial groupoids.}, journal = {Semigroup forum}, pages = {246--254}, publisher = {mathdoc}, volume = {6}, year = {1974}, zbl = {0262.20067}, url = {http://geodesic.mathdoc.fr/item/SF_1974__6_133980/} }
A.H. Clifford; T.E. Hall. A characterization of ...-classes of semigroups as partial groupoids.. Semigroup forum, Tome 6 (1974), pp. 246-254. http://geodesic.mathdoc.fr/item/SF_1974__6_133980/