@article{10_4171_ggd_113,
     author = {Stephen J. Pride},
     title = {Universal diagram groups with identical {Poincar\'e} series},
     journal = {Groups, geometry, and dynamics},
     pages = {901--908},
     year = {2010},
     volume = {4},
     number = {4},
     doi = {10.4171/ggd/113},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/113/}
}