@article{SLC_1989_21_a9,
     author = {Gilbert Labelle},
     title = {Le d\'enombrement de structures asym\'etriques},
     journal = {S\'eminaire lotharingien de combinatoire},
     year = {1989},
     volume = {21},
     url = {http://geodesic.mathdoc.fr/item/SLC_1989_21_a9/}
}