@article{SF_1996__53_2_135487,
     author = {M. Kilp},
     title = {Perfect monoids revisited.},
     journal = {Semigroup forum},
     pages = {225--229},
     publisher = {mathdoc},
     volume = {53},
     number = {2},
     year = {1996},
     zbl = {0865.20053},
     url = {http://geodesic.mathdoc.fr/item/SF_1996__53_2_135487/}
}