@article{00907651,
title = {An extension of the exponential formula in enumerative combinatorics.},
journal = {The Electronic Journal of Combinatorics [electronic only]},
volume = {3},
year = {1996},
zbl = {0856.05003},
language = {en},
url = {http://dml.mathdoc.fr/item/00907651}
}
Labelle, Gilbert; Leroux, Pierre. An extension of the exponential formula in enumerative combinatorics.. The Electronic Journal of Combinatorics [electronic only], Tome 3 (1996) . http://gdmltest.u-ga.fr/item/00907651/