@article{SLC_1987_18_a7,
     author = {V\'eronique Bruy\`ere},
     title = {Factorization of {Prefix-Closed} {Subsets} of {Words}},
     journal = {S\'eminaire lotharingien de combinatoire},
     year = {1987},
     volume = {18},
     url = {http://geodesic.mathdoc.fr/item/SLC_1987_18_a7/}
}