@article{SLC_1990_25_a11,
     author = {Peter Kirschenhofer},
     title = {Enumeration of {Trees}},
     journal = {S\'eminaire lotharingien de combinatoire},
     year = {1990},
     volume = {25},
     url = {http://geodesic.mathdoc.fr/item/SLC_1990_25_a11/}
}