@article{SF_1979__18_134336,
     author = {C.C. Edwards},
     title = {The {Minimum} group congruence on an ...-unipotent semi group.},
     journal = {Semigroup forum},
     pages = {9--14},
     publisher = {mathdoc},
     volume = {18},
     year = {1979},
     zbl = {0422.20047},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__18_134336/}
}