@article{MOMA_1988__106_1_178400,
     author = {K.H. Hofmann and W.A.F. Ruppert},
     title = {The {Foliation} of {Semigroups} by {Congruence} {Classes.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {179--204},
     publisher = {mathdoc},
     volume = {106},
     number = {1},
     year = {1988},
     zbl = {0671.22003},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1988__106_1_178400/}
}