@article{ADM_2007_3_a8,
     author = {Emilia Giraldes and Paula Marques-Smith and Heinz Mitsch},
     title = {$F$--semigroups},
     journal = {Algebra and discrete mathematics},
     pages = {67--86},
     publisher = {mathdoc},
     number = {3},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2007_3_a8/}
}