On the Real-rootedness of the Descent Polynomials of $(n-2)$-Stack   Sortable Permutations
  B\'ona conjectured that the descent polynomials on $(n-2)$-stack sortable permutations have only real zeros. Br\"and\'en proved this conjecture by establishing a more general result. In this paper, we give another proof of Br\"and\'en's result by using the theory of $s$-Eulerian polynomials recently developed by Savage and Visontai. 
Philip B. Zhang
math.CO