@article{MAN_1992__293_4_164956,
     author = {J.W. Cannon and Ph. Wagreich},
     title = {Growth functions of surface groups.},
     journal = {Mathematische Annalen},
     pages = {239--258},
     year = {1992},
     volume = {293},
     number = {4},
     zbl = {0734.57001},
     url = {http://geodesic.mathdoc.fr/item/MAN_1992__293_4_164956/}
}