@article{JAC_2005__22_4_a1,
     author = {Aguiar, Marcelo and Sottile, Frank},
     title = {Cocommutative {Hopf} algebras of permutations and trees.},
     journal = {Journal of Algebraic Combinatorics},
     pages = {451--470},
     publisher = {mathdoc},
     volume = {22},
     number = {4},
     year = {2005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JAC_2005__22_4_a1/}
}