@article{SLC_2008-2010_59_a4,
     author = {Jean-Christophe Aval},
     title = {Keys and {Alternating} {Sign} {Matrices}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {59},
     year = {2008-2010},
     url = {http://geodesic.mathdoc.fr/item/SLC_2008-2010_59_a4/}
}