Matthieu Josuat-Vergès Jean-Christophe Novelli Jean-Yves Thibon The algebraic combinatorics of snakes. 1613-1638 2012 119 J. Comb. Theory, Ser. A 8 http://dx.doi.org/10.1016/j.jcta.2012.05.002 db/journals/jct/jcta119.html#Josuat-VergesNT12