@article{SLC_2006-2007_54_a1,
     author = {Ira M. Gessel},
     title = {Symmetric {Inclusion-Exclusion}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {54},
     year = {2006-2007},
     url = {http://geodesic.mathdoc.fr/item/SLC_2006-2007_54_a1/}
}