@article{10_4153_CMB_2010_063_2,
     author = {Chapoton, Fr\'ed\'eric},
     title = {Free {Pre-Lie} {Algebras} are {Free} as {Lie} {Algebras}},
     journal = {Canadian mathematical bulletin},
     pages = {425--437},
     year = {2010},
     volume = {53},
     number = {3},
     doi = {10.4153/CMB-2010-063-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2010-063-2/}
}