@article{SF_1995__50_3_135365,
     author = {P.A. Grillet},
     title = {Stratified semigroups.},
     journal = {Semigroup forum},
     pages = {25--36},
     year = {1995},
     volume = {50},
     number = {3},
     zbl = {0822.20059},
     url = {http://geodesic.mathdoc.fr/item/SF_1995__50_3_135365/}
}