@article{JIS_2003__6_4_a7,
     author = {Callan, David},
     title = {A combinatorial derivation of the number of labeled forests},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {6},
     number = {4},
     year = {2003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2003__6_4_a7/}
}