@article{SF_1979__17_134331,
     author = {R. Feigenbaum},
     title = {Regular semigroup congruences.},
     journal = {Semigroup forum},
     pages = {373--378},
     year = {1979},
     volume = {17},
     zbl = {0433.20043},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__17_134331/}
}