@article{SLC_2009-2011_61A_a2,
     author = {Sylvain Lavall\'ee and Christophe Reutenauer},
     title = {Characteristic {Polynomials} of {Nonnegative} {Integral} {Square} {Matrices} and {Clique} {Polynomials}},
     journal = {S\'eminaire lotharingien de combinatoire},
     year = {2009-2011},
     volume = {61A},
     url = {http://geodesic.mathdoc.fr/item/SLC_2009-2011_61A_a2/}
}